After finally getting FlashBuilder to successfully edit and debug Flash Professional projects I was feeling quite triumphant, not to mention ecstatic that I could get all the nice bells and whistles of the Flashbuilder debugger while publishing to Flash Pro! All was good for about three days, and then, in standard fashion, Flashbuilder just forgot how to debug my files and refused to open them in anything but Flash Pro! This was completely out of the blue. I published once and Flashbuilder played nicely, launched the debugger, and let me inspect my properties. I launch again, and it opens the file in Flash Pro with no debugging!!!
After a few minutes of banging my head into the nearest table top, I took a deep breath, counted to 10, rebooted my computer, and said a little prayer. Unfortunately, Flashbuilder was still hosed after the reboot. I then asked the Googs for some help. Not much luck their either. Finally, I decided to pull a hail-mary and open up Flashbuilder preferences. Here I finally had some success!
What happened: Flashbuilder lost track of where to the Flash Debug Player lives.
How to Fix it: Open FlashBuilder Preferences -> Flash Builder -> Debug and look for the input for “Standalone Adobe Flash Player (debug version)”. Click on browse, then browse your standalone Flash Player Debugger. Click ok, and run debug on your project! That should fix the issue (at least it did for me).
If you don’t have the standalone Flash Player Debugger installed, you can download it from Adobes site and unpackage it anywhere on your machine, then just point at the file and you’re good to go (hopefully).