My Firefox bookmarks disappeared or were deleted (most of them) after an automatic update to Firefox 3. To find a backup and recover the missing files, I did the following import / reinstall trick. (I use Windows XP).
I hope it works for you, but don't come after me if it doesn't ;-)
2. Type in (or cut from here and paste in):
3. Windows Explorer opens a folder called “Profiles” containing... your profiles... of course.
4. Double-click the profile folder you wish to open –I only had one folder, but others apparently have several. Mine was named “xxxx.default” folder where “xxxx” stands for some random numbers, which I probably shouldn't print on the internet... maybe. Anyway, open that folder.
5. Then open “bookmarkbackups”
There should be 5 Firefox files in there named “bookmarks” and with a date.
6. Open the oldest one.
Hopefully you’ll see a page with all your old bookmarks listed on it.
7. Close that Firefox file, then save a copy of it to your desktop.
8. Open Firefox. Go to Bookmarks>Organize Bookmarks
The “Bookmarks Manager” should open.
9. In “Bookmarks Manager” go to File>Import
Chose “From File”.
10. Find the Firefox “bookmarks-2008-08-05” file on your desktop and double click on that.
Voila! The bookmarks should be restored in Firefox now. You might have some double-ups which you can delete.
If you still have problems, this link will take you straight to the support page where everybody is complaining about this problem.
It’s a big pain, I know, so I hope this helps.
*Screen shots courtesy of the Firefox knowledge base, although I used a different technique to fix it than they did..