After upgrading (regular upgrade from Jaguar) to Panther, I found that Illustrator and Photoshop wouldn't load properly. After trying to start the apps, the spinning beach ball would appear and the app would do nothing.
I tried trashing prefs, re-installing both apps, etc. Nothing worked. The solution? Delete the Workflow folder located at /Library -> Application Support -> Adobe/. This fixed the problem!
Mac OS X Hints
http://hints.macworld.com/article.php?story=20031113162801468