Flex Builder 3 Debugger Stopped Working!!

Posted: March 10, 2008 in Adobe, AIR, Flex


I’ve come to point where I exhausted all options … at least the ones I am aware of. After having my Flex Builder 3 working for the past week, the debugger has suddenly stopped working. If I debug the app I am working on, the browser will open, the app will run BUT the Flex Builder will not connect to the debugger. How do I know this?

  1. None of my Breakpoints will stop the execution of the app
  2. According to the Progress panel in Flex Builder, I see the message “Waiting for Flash Player to connect to debugger”

At around 91% I get the dialog box that tells me the Launch Failed, Ensure that: 1. You compiled your Flash application with debugging on. 2. You are running the debugger version of Flash player.

Now I have spent 3 hours trying every option I can think of. I have restarted the laptop 4 times already. But just in case I may have missed something here is a list of the things I have tried;

  • Uninstalled the Flash Player (restart laptop).
  • Installed the Debug Flash Player (from the Adobe web site) .
  • Tried both Firefox 2 and IE 7.
  • Uninstalled the Flash Player (restart laptop again).
  • Installed the Debug Flash Player from the Flex 3 SDK.
  • Tried both Firefox 2 and IE 7.
  • Uninstalled Flex Builder 3. (restarted laptop yet again).
  • Installed Flex Builder 3.

Still no luck. The last thing I did was to create a small app that reported the Flash Player version. Here is the code for that app;

<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml" layout="vertical">
import flash.system.Capabilities;

private function reportVersion():String {
if (Capabilities.isDebugger) {
return "You are running the Debugger version of the Flash Player";
} else {
return "You are running the Non-Debugger version of the Flash Player";
private function reportType():String {
return Capabilities.playerType + " (" + Capabilities.version + ")";

<mx:Label text="{reportVersion()}"/>
<mx:Label text="{reportType()}"/>

Yes, the app tells me that I am running the Debugger version of the Flash Player. Now what?? I have found the Debugger in Flex Builder to be an invaluable asset in developing Flex/AIR apps and learning Flex. Without it I find myself severely disabled.Now here’s the really strange part … The debugger works when debugging an AIR application.

I’d like to say that I blame Vista (I hate Vista) but I must give it break this time and say, I doubt it.

This is truly a mystery and Scooby Doo is nowhere to be found. Is there anyone out there with a clue?

Thanks and Ciao

  1. Tony Fendall says:

    One thing I have found in the past, is that uninstalling the flash player through the windows control panel doesn’t work. You need to download the flash player uninstaller from the adobe site (same page you download the players from). If you haven’t tried this yet, then I expect that will fix it for you.

    Beyond that I’m not really sure. Possibly something else on your computer is capturing the port which flex builder is trying to use to connect to the flash player.

    Hope that helps

  2. therush says:

    Hi Tony,

    About 30 minutes later, one uninstall (using the Adobe uninstall), one reboot later, and one more install of the Debugger Flash Player (9.0.115) … still no go.

    I read a post saying that the Flex debugger uses port 3434. The documentation says 7935. I explored my security settings to make sure that neither port is not being blocked.

    I think that this all started when the Adobe updater started earlier today. It stated that it would take about 2 hours to download and install all of the CS3 updates. I allowed it to continue until about 27 minutes was left. I then paused it and restated the laptop …

    still trying to troubleshoot this problem.

  3. Seth says:

    try this, if you’re on XP open this file: C:\Documents and Settings\[user name]\mm.cfg
    (Not sure exactly where this will be in Vista)

    If this file contains a line like “…3/.metadata/.plugins/com.adobe.flash.profiler/ProfilerAgent.swf?host=localhost&port=9999” remove that line. Save the file and you should be okay.

    I ran into a problem that sounds similar. It seems to be caused by trying to use the profiler with FireFox, if the profiler failed it would leave this text entry and debugging would stop.

  4. therush says:

    Hi Seth,

    Sorry, no such line in that file. It contains only two lines; ErrorReportingEnable=1 and TraceOutputFileEnable=1.

    Since my last comment I have; uninstalled the Flash Player, uninstalled Flex Builder 3 (including removing all traces on hard drive and registry), restated laptop, installed Flex Builder 3 (trial without serial number), and disabled all firewalls. Still no luck. This really sucks and I am about ready to trash the laptop.

  5. Jeff Houser says:

    Did you try cleaning your project? Did you try creating a new project (and/or workspace) with a simple application?

    I’ve also seen this occur inconsistently due to code oddities. For example could you have metadata in some component that uses double quotes instead of single quotes (or vice versa, I forget which is the problematic one)? Start commenting out code to see if that helps address the issue..

    If you search on Flex Coders Yahoo Group you may find some tips.

  6. Seth Bienek says:

    I had this problem a couple of weeks ago. After much hair-pulling, reconfiguring, and praying to the Gods for mercy, creating a new project fixed the issue.

    At least I think that fixed the issue, it was the last thing I tried before the debugger started connecting again.

    Hope it helps!

  7. Paolo says:

    Do you have nod32 3.x installed, I had the same problem and after much pain I discoverd that was nod32 to block the debugger. If that’s your case you have to go to nod32 setting and select http/webbrowser and remove the check from the browser you are using to debug.

  8. therush says:

    Hi Paolo,

    Yes I do have Nod32. I first thought that this was the reason. However during my troubleshooting I disabled Nod32 AND the Windows firewall in order to isolate the issue.

    Thanks for all the help everyone. I found the solution and resolved the issue. You can see my most recent post for the resolution.


  9. Jason says:

    Interesting. I have the same problem with an AIR application that won’t connect to the debugger (yes, I’ve seen it with Flash/Flex apps also). Unfortunately, there’s no context menu for AIR apps to check the debugger state. Anybody else run into this or have a suggestion?

  10. HBalage says:

    Same problem, no reinstall, no project recreation helped. The solution was: after starting the debug session, i click with right buttom on the flash plug-in in the browser, selected the Debugger item, a dialog apperd, i entered in the custom field than ok, and everything got work alright! And from that time the debug sessions get connected automaticaly as have to be!

  11. Tiggrou says:

    Hi, I tried something like Hbalage said : I set the local machine as debugger host. That didn’t solve the problem, but when I edited debugger options from my project settings (set run in background to false), it worked. Now everything works fine.

  12. mark says:

    thank you for help all friend , i should setup Nod32 on my laptop for helping.

  13. scott says:

    Commenting out that line in mm.cfg fixed it for me, on OS X.

    Found reference to that in labs.adobe.com, referencing external AIR app, but I simply had debugger die, after doing some profiling.


  14. Ji says:

    I encountered the same problem, and after trying for 3 hours, now I’ve fixed it.
    Try this: Select Window->Web Browser->Internet Explorer, instead of others (firefox, etc). This helps on my machine (Windows XP/Flex Builder 3/Flash Player Debug version).
    The Flash Player Debug version is download from http://download.macromedia.com/pub/flashplayer/updaters/9/flashplayer_9_ax_debug.exe. It is an activeX controls, and can only be used in IE. Another one (http://download.macromedia.com/pub/flashplayer/updaters/9/flashplayer_9_plugin_debug.exe) can be used in firefox, but it seems to have some problem with debugging.
    Wish this can be of some help.

  15. biril says:

    Ji’s solution works for me too. When I debug in Firefox, Flex Builder can’t connect to the debugger, while there’s no problem with IE..

  16. naveen says:

    I was facing the same issue withe Debugger in Flex builder3, where it wouldn’t debug the application and finally I got it working by changing the web browser from firefox to IE. In order to that goto window > preferences> General> Editors > Web browser

  17. AJQ says:

    Have the same problem, just seemed to stop debugging in FF for no reason… I did install XAMPP, wondering if that could haave affected anything. working fine in IE 🙂 what a pain.

  18. AJQ says:

    Update: I just realised what the problem was, the IE Tab extension for Firefox breaks the debugger, hope this helps.

  19. Steve Brewer says:

    Was having this problem with flex building an AIR app – deleting everything under bin-debug, then cleaning the project seems to reliably get things back on track for me.

  20. had the same problem yesterday. The problem is that i could have sworn it was working for the past seven days with the same configuration. FF 3 + IE Tab etc etc. After a few hours of total chaos where i actually started pulling a few hairs out, i figured out that the IE Tab was the culprit. To make matters worse, i was offline while doing this and couldn’t chance upon blog articles such as this for pointers. C’est la vie .. 🙂

  21. maloola says:

    had the same problem. using flex builder 3, win xp and nod32 v3. first i tried reinstalling EVERYTHING, than switching workspaces and changing/recreating projects.
    to fix this, open the advanced mode in nod32 (in the bottom of the menu), choose the tools, go to the quarantine, and restore the adobe threaded .dll =\

  22. cluigi says:

    I had the same error, it was a syntax error in the “index.template.html” file

    the flash animation could’nt load and then flash debugger can’t connect to flash animation….

    hope this helps


  23. ashok says:

    the solution provided by Ji solved the issue on my system

    “I encountered the same problem, and after trying for 3 hours, now I’ve fixed it.
    Try this: Select Window->Web Browser->Internet Explorer, instead of others (firefox, etc). This helps on my machine (Windows XP/Flex Builder 3/Flash Player Debug version).
    The Flash Player Debug version is download from http://download.macromedia.com/pub/flashplayer/updaters/9/flashplayer_9_ax_debug.exe. It is an activeX controls, and can only be used in IE. Another one (http://download.macromedia.com/pub/flashplayer/updaters/9/flashplayer_9_plugin_debug.exe) can be used in firefox, but it seems to have some problem with debugging”

    thanks for all this information.

  24. istrasci says:

    To anyone for whom the debugger has stopped working in Firefox and none of the above solutions have worked for them, I made a huge (at least in my mind) discovery… Debugging stopped working for me based on one or more of my Firefox extensions… I did a fresh Firefox install and I could debug fine, but when I added my extensions back (which I should have done one at a time), it wouldn’t work… I’m running Firefox 3.0.2 with the extensions:
    – Google Toolbar 3.1.20080730W
    – FireGestures 1.1.5
    – Tab Mix Plus 0.3.7pre.080920
    – Aero Silver Fox Basic 3.0.1
    I suspect that the guilty extension is the Tab Mix Plus, as it is still a beta for Firefox 3…

    Anyway, my solution is to run the Firefox profile manager (make sure Firefox isn’t running, then: Firefox.exe -ProfileManager) and create a new profile for debugging (name it whatever you want)… Then in Flex Builder 3, go to Window -> Preferences -> General -> Web Browser… Click the Firefox (the words, not the checkbox) to highlight it, and then click Edit… Under the Edit menu, under the ‘Parameters’ section, add the following:
    -P “”
    Make sure the ‘P’ is a capital P and make sure to include the quotes too…

    This makes Firefox execute using that profile… And with the base profile (no extensions, etc.) debugging should work just fine… This drove me crazy for weeks, so I hope this is of use to someone!!!

  25. istrasci says:

    Oops, HTML chopped something out… The parameter should read:
    -P “[name_of_debugging_profile]”

  26. Hello says:

    Can’t debug with Firefox because IT SUCKS..


  27. MarkJ says:

    Same for me with NOD32, thanks Paulo


  28. Jan says:


    i have a soulution for my problem “Waiting for Flash Player to connect to debugger”
    i had disabled the Project -> Build Automaticly. Since i disabled it, the flexbuilder cant connect to the flashplayer. When i enabeld Build Automaticly, it is working. Very strange.

    My System, vista 64bit

    best regards from germany

  29. debuggerFan says:

    I’ve had the same problem sever times deleting the C:\Documents and Settings\[user name]\mm.cfg file usually works but recently it was even worse. The only thing that worked was cutting all the code from the main entry point of my app, saving, then pasting it back in and saving again.. that saved me importing the code as a new project

  30. RichClient says:

    Same problem started for me today (on XP). And tried almost everything suggested here. I have a Firefox that has no add ons, except for the flash player and debugger. Tried IE (setting it in Flex Builder as the default browser.) Tried deleting the mm.cfg file. The only thing I have to say different is that my Flex has been cumulatively acting “fishy”.

    For example, I’ll create a component in another project, reference that component directory in my namespace (yada) and put the component on the form. It runs just fine, but when I go into the “design” view of the application, the component appears as a red box with an “X” in the middle. Then I’ll bounce the Flex Builder and the component appears correctly in “design” view. Stuff like this has been getting worse and worse. Components that are based on have lost their identity, and unless I close the projects that have those components, I cannot get a clean compile on the main application I am working on.

    Does anybody have connections at Adobe? This is really bad, no debugger. I feel somewhat violent about this because it is such a show stopper. What, I’m going to do “Alert.show” for the rest of my life?

    Help please!

  31. RichClient says:

    That last post should have said “components that are based on Canvas”

  32. Steve says:

    Seth’s suggestion worked for me. I have been alternately using the profiler and debugger, and I guess at some point the mm.cfg file got corrupted.

    Thanks Seth!!!

  33. Eduardo Miano says:


    valew por essa solução.
    Instalei e desintalei milhões de vezes o flex.


    I am from Brazil!!!!


  34. Daniel Esono says:

    I ‘ve the same problem with Air App I can’t use the debbuger, Flex Builder is waiting for Flash Palyer to connect to debugger, although the applicaction works perfectly. And if I close the application I can see a Launch Failed Flex message where I can see all the traces, but I can’t debug.

    Thanks in advance

  35. Scott says:

    I’ve wasted about 2 weeks on this issue…

    Environment: Vista Business, Coldfusion, MySQL and Flex 3

    I’m not exactly sure what caused the issue; I was not developing for about 3 weeks in Flex and when I came back to it I discovered my debugger was gone. I believe I had updated my flash player during that time but I can’t be 100% sure.

    I’ve uninstalled flash, (restarted) re-installed flash 10 and debugger and still the same issue. I am running Coldfusion on my notebook.

    After reading a few posts above and a couple of other ideas elsewhere I decided to create a new project. I just did a really basic display my flash version. Set a breakpoint and debugged. To my amazement it worked! However, when I went back to my original project it still did not work. So my guess is that there’s something wrong with my project even though I didn’t do anything with it.

    I renamed the bin-debug directory and recompiled but had the same issue; it’s unable to connect to the debugger.

    One more piece… I’ve noticed that if I “crash” a flex application somehow, coldfusion holds open the files and I can’t do a project -> clean; it says the files are in use. Now, this is also true when I try to debug an application. I have to toggle over to the CF administrator and clear the cache then apply settings and it frees up the flex application to be cleaned.

    A thought has crossed my mind to drop the project and re-create it by cut and paste to see if the problem goes away. But another part of me really wants to know what the issue is; after reading these posts I don’t think this will be my last encounter with the issue.

  36. Lane says:

    ahhh ..
    all solution above no go for me ..
    my situation are same ..

  37. […] Builder Debugger stops working By rostanin In Flex Builder 3 Debugger Stopped Working!! people identified a lot of reasons that can lead to the erroneous behaivior of the debugger in the […]

  38. Juha says:

    If your Flex Builder (Windows) stopped debugging around March 9, you may want to check this page:


    I know it’s about Silverlight, but the fix on that page also fixed my Flex debugger.

  39. ady dharmadi says:

    I’ve tried solution from Juha and it’s works :), thank you very much

  40. satish says:

    Thanks, it worked for me also

  41. […] google了一下,最后在https://therush.wordpress.com/2008/03/10/flex-builder-3-debugger-stopped-working/上面找到了答案,非常感谢Juha网友的答复,其原文内容是 […]

  42. kirk says:


    this link has a solution that work for me

  43. Ashish Desai says:

    yes, i was using opera browser and then i read the item number 10 above – “10. HBalage – March 26, 2008

    Same problem, no reinstall, no project recreation helped. The solution was: after starting the debug session, i click with right buttom on the flash plug-in in the browser, selected the Debugger item, a dialog apperd, i entered in the custom field than ok, and everything got work alright! And from that time the debug sessions get connected automaticaly as have to be!” and this did solve my problem. thanks a lot.

  44. Paul Feakins says:

    Fixed for me by right-clicking the Flash movie, choosing debugger and then setting the IP to Thanks!

  45. ivanz says:

    Nothing from the above fixed mine.

    But this fixed it:
    Under the bin-debug folder, I did not see any .html pages being created, there were only .swf files. The project was copied from somewhere else, so I just grabbed the missing .html page and dropped it into the bin-debug folder corresponding to the .swf file I was trying to debug and it worked.

    Surprisingly, building the project or debugging it did not create only .swf files but no .html files.

  46. John says:

    I was having similar problems today (on Vista, IE) but discovered that my flash debugger version (10) didn’t match that of the debugger in Flex Builder 3.2 (9). I simply uninstalled the active X plugin and installed version 9 from the FlashPlayer website – http://www.adobe.com/support/flashplayer/downloads.html#fp9. Odd that the latest version of Flex Builder doesn’t use the latest flash debugger but that solved it for me anyway.

  47. mike says:

    Cooment 10. HBalage was right. This fixed my web and desktop debugging problems. run a debig version of a web project(create a new one if need be) then right click debugger option and enter the ip address and click connect. All problems solved! thanks HBalage

  48. I am still having this issue, I already:
    Completly uninstalled, Flex, and Flash, and reinstalled latest version, I also did this, plus installing the debugging version.

    I am desperate! Can anyone help?

    I am running Flex Builder v3.0 on Vista 64bit.

    My builder on mac, works perfectly.

  49. Dustin says:

    well, I have tried some of the things mentioned above. Thanks for everyones posts.

    I found one bug in Adobes Jira going back to 2007 about this issue in Flex Builder.

    Oddly, I am having trouble launching a specific Air app in both debug and run mode. If I launch another Air application in the same project, I can successfully open it. Also, the one which is “broken”, actually does launch, but it launches in “the background”- even though my project is set to not do this and other air apps in this project don’t do this. I can tell its running since I see the console log and also Adl.exe is running for each instance I launch.

    —scratching my head…

  50. sami says:

    I started having this problem around the time i installed nod32 – not sure why but my application server type changed to webhost instead of \”none\” – which meant it tried to load the file from http://localhost:8080/file.html instead of c:/project/file.mxml

    i will create a new project and move the files there since i cannot locate, at the moment, how to change application server type

  51. […] 40. Juha – March 19, 2009 […]

  52. Pierre says:

    I was having the same problem with launching an AIR APP in run and debug mode. I finally changed the application version in the
    -app.xml file to:

    and all runs well in version 10

  53. Pierre says:

    In my prior post the delimiters deleted the text

    “your app name”-app.xml file to:
    application xmlns=”http://ns.adobe.com/air/application/1.5.1″

  54. Craig says:

    I also have this problem with as yet no resolution. Why does flex buider ide suck so much the output from it is near useless 😦

  55. sami says:

    i uninstalled nod32 and created a new project and copied the files there, this time making sure the project was set to use “no server” – and it worked, atleast for my app

  56. Novian says:

    Has anyone figured out a solution for getting the Debugger to connect via either Firefox or Safari on a Mac OS X 10.4.11? I’m using Flex Builder 3 and I cannot make a debugger connection for the life of me.


  57. I have the Mac OSX version of this solution on my blog if anyone’s interested. JynxStudio

  58. Ran into this same issue today…spent more time on it than I wanted to (~45 min). Eventually, I deleted the project. I checked it out again from our svn repository, rebuilt it and it worked!

  59. Barjawi says:

    Post number 10 from HBalage worked for me. Thanks all.

  60. Frazko says:

    I had the same problem with an AIR app, when i created a new project.. it worked.. so.. i checked the -app.xml file and there was a difference with xmlns
    it was like this:

    and the new project was like this:

    i changed it.. and it worked out!!… I hate it!!!

  61. Frazko says:

    mmmm .. didn’t showed up..
    my app:

    new proyect:

  62. Nick says:

    @Seth (#3) – You saved me! I spent an hour searching for this solution!

  63. Yoeran says:

    I just ran into this problem too. However, it does work when I direct it to my browser. Debugging won’t work when I launch it as a .swf. Very, very annoying..

    I can’t seem to find any “Debugger options” as #10 from HBalage mentioned.

  64. Dano Manion says:

    I was having the same issue on OS X 10.5 with Flex Builder 3.

    I Solved it by setting the Flash movie default to flash player 10.
    I figured out that Flex was calling an old ‘flashplayer.app (8)’ by default, so I simply changed the default to ‘flashplayer.app (10)’ and everything seems to be working now.

    A cheap way to do this is to:

    1 – Find any .swf on your system
    2 – Right-click on it
    3 – Select ‘Get Info’
    4 – Go to where it says “Open with”
    5 – Find ‘FlashPlayer.app (10 )’ in the list an select it
    6 – Click on the “Change All… ) Button

    Hope this Helps!

  65. colin says:

    yes, this sucks. please vote for better player management:


  66. tekitwa says:

    I think the pb is an os pb
    the debugger is using localhost and not

    just add this line to the hosts file : localhost

    if any pb :

    Works for me !!!!

  67. jk says:

    I just got this , i copied my main application code to another file and it runs fine

  68. bwilgus says:

    fixed it on my end. had to recopy my “AC_OETags.js” and “playerProductInstall.swf” files into my “html-template” folder so they would be included in the next compile into my bin-debug directory.

  69. steve says:

    Google Chrome users – here’s what you’ve been looking for:


  70. Felisberto Lagartinha says:

    I have the same issue than 66. My applications run with non-debug even if i click debug.
    I have tried everything that is said here, from anti-virus, to the hosts file (good catch), reinstaling everything and changing the browsers, installing the debugers on firefox and IE.

    Nothing worked. Shouldn’t we be able to setup the debugger by hand if need to? My breakpoints appear as a broken dot instead of a dot when i create them, this means that the IDE knows the debbuger is not working, but i can’t understand why.

  71. #10 worked for me, thanks a bunch!

  72. lovethelanguage says:

    #10 (HBalage) worked for me as well. Thanks!

  73. Shaula says:

    If you Installed flash debugger, go to IE and right click on some flash page, than click on debugger, check Localhost and click on Connect… if you get some error massage, Ignore it and try to Debug via FB… It worked for me

  74. link says:

    Hey There. I found your weblog using msn. That is a very neatly written article. I will make sure to bookmark it and come back to read more of your helpful information. Thank you for the post. I will definitely return.

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