C:\Documents and Settings\~name~\Application Data\Mozilla\Firefox\Profiles\~random letters~\bookmarkbackups
I'd suggest copying this entire folder to another location, just in case any of your files are corrupted from the problem you're having now.
After you reinstall, go to Bookmarks -> Organize Bookmarks, click Import and Backup, then go to Restore -> Choose File. Now go to where you saved that folder and select the most recent bookmark backup file.
Also, in your profile folder, theres a file called bookmarks.html, which you might want to save as well before the clean install. It's likely to be a redundant file, but better safe than sorry should something go wrong (or I'm giving bad info, which I really hope I'm not).
It looks like your add-ons are saved in C:\Documents and Settings\~name~\Application Data\Mozilla\Firefox\Profiles\~random letters~\extensions, but really I don't know how that's going to help you. If nothing else, it should give you a name to search for after the reinstall if you can't find a way to carry them over.
Hope some of this helps :sweat: