Go to:
CDocuments and Settings\[username]\*Application Data\Mozilla\Firefox\Profiles\[profilename]\
* indicates hidden folder
Look for your bookmarks.html file. Double-click it and see if you have your bookmarks there. If so, then back it up and then import them in FF.
There might also be a bookmarks.bak file which contains all your bookmarks and what not. (If the .bak file contains your bookmarks, then delete the bookmarks.html file and rename the bookmarks.bak file to bookmarks.html)

That's all I can think of.