Sorry, I forgot to say I use Flash CS4.
I would be glad to have answers from other people than me, because in each of my thread i feel like i'm doing a monologue. Maybe some adobe people ?
Finally I ended up to think the cause of the problem is the use of SWC libraries. It prevents the code from being stoped, even before entering the code within the library.
For the ones which encountered the same problem as me, I found an other problem in relation with this one.
Sometimes, when you launch an application in debug mode in Flash, even without use of externals swc, the compiler stop on breakpoints, but the little yellow arrow that should appear in this case doesn't. And even if you launch the debug mode again, it doesn't appear. In this case you could think the compiler didn't stop. But at this time, if you open the debug console and do a step by step, the yellow arrow will show and will do it every next time you launch the debug mode.
One tips to be quickly aware of the problem is to drop breakpoints in the constructor of the document class, because the Flash Player won't show before this constructor is fully processed.
It happens to me all the time since I jumped to Flash Pro CS4. It makes the work very hard. I work on a pretty big project. No SWC libraries in my case, all my AS3 logic is outside of the .fla file - in a dozen of .as class files. I set breakpoints in the classes script, but hardly ever the breakpoints do stop, although I know the breakpoint-marked lines are executed (which I check by trace() or simply see the results). Some breakpoints are set in class constructors, some are in functions that are called by constructors, but also some are just normal functions or mouse event handlers. I might say about 10% cases of breakpoints do stop as expected, the rest is just ignored.
My configuration: Flash CS4 Pro 10.0.2, Windows XP SP3, I have also older versions of Flash installed (but not run simultanoeously) on the same machine if that matters.
It would be really great if someone from Adobe had check that issue, because debugging big projects with trace() only is pretty tiresome and time-consuming.
I'm back but I have still not found the cause of the problem.
I answered if the fact I work on a server could be the cause, but moving my files to local didn't resolve the problem.
I also have the problem sometimes even without using swc libraries, just with as3 source files.
I even tried to add the breakpoints manually in the Flash's xml debug file but successless.
However, I found a little trick that can be helpful. When the debugger bugs like that, instead of adding breakpoints, I throw Errors, and then the debugger stop on the line where the error is thrown, giving you access to the content of all the variables at that point. But you still cannot use step by step.
Nice trick with throwing Error, pretty helpful when breakpoints fail to do their jobs
Hopefully one day Adobe will fix the debugger to be as functional as it was before
Finally I found a solution :
Throw an error in the code and let the debugger catch it, it will open the source file. You can now set breakpoints that will works. Delete the error throwing and the job is done.
PS : During the time I had this problem, I looked for external debuggers on the web. But I didn't found any which could set breakpoints or display the content of private variable cause the most are based on LocalConnection. So if anyone knows a good external debugger...
I'm having this same problem with Flash CS5. And throwing the error didn't seem to fix it. It stopped there but all variables were blank. I reinstalled, cleaned my registry but nothing seems to do any good. Help please.
I am having the same problem with a complex (multiple .swf) application and finally found a "fix". Specifically my problem was that the debugger suddenly would stop Stepping Into or Continuing into the next .swf file in the process.
My solution was to set a breakpoint in the second .fla (.swf) file and 1) just run the debugger from the point of the second .fla source file until it hit the breakpoint there. then 2) once it successfully hit the breakpoint, then I could restart the debugger starting from the first .fla file and start debugging from that point and it was then able to continue debugging into the second .swf when called.
Hope that can resolve your issues, too.