http://kb.mozillazine.org/Profile_Manager#Warningabout:support
Help -> Troubleshooting Information. Clicking on that link launches an enhanced version of the profile manager. That is the easiest way to launch the profile manager. If you do that you don't need to read the rest of this KB article
Give FF a tuneup:
Refresh FF...Removes addon's restores settings to default.
How do I get those addon's and settings back?
Try Safe Mode - restarts with addon's disabled
How do I get my addon's back if I want them next time?
Try clearing the startup cache - restarts clearing cache.
How do I regain cache? Seems like I did that once before and spent a lot of time fiddling to get back to normal.