Ouch.
I'd delete your profile folder and start from scratch.
To do this go to
C:\Documents and Settings\YOUR USERNAME\Application Data\Mozilla\Firefox\Profiles\XXXXXXX.default, copy your bookmarks.html and cookies.txt to your desktop then delete the entire
C:\Documents and Settings\YOUR USERNAME\Application Data\Mozilla\Firefox\Profiles\ directory.
Install Firefox, start it up then close it as soon as you see the start page.
Copy bookmarks.html and cookies.txt into the new profile directory and you're sorted.
