I ran into a strange issue with the Flex debugger today. Basically, it would take a long time for the swf file to be connected to Flex builder's debugger.

I checked the port usage (netstat -ano), didn't see anything suspicious -- I am seeing Flex is listening on port 7935, which is a correct behavior when debugging Flex app (Flex basically listens on that port, and the debug version of Flash plugin would attempt to connect to that port upon launch).

I checked mm.cfg, didn't see anything strange there. Looked at hosts file, looked good (127.0.0.1 is mapped to localhost). Tried installing a new version of Flash debugger plugin, no go. Cleaned the project, it didn't refuse to work. Finally, I tried to debug things with a different Flex project, and it worked fine! I looked at the difference between the two projects and the only difference is that one is a project running locally, another one is running through Apache + ColdFusion via a virtual host. A quick look at the services in the service browser (type services.msc in Run dialog box) and I saw that ColdFusion Application Server had been stopped. I restarted it and voila, everything worked like before!

While looking for a solution, I also came upon the link below, it didn't end up helping me, but it might to someone out there.

http://therush.wordpress.com/2008/03/11/resolved-flex-builder-3-debugger-stopped-working/