Comment 22 for bug 241609

check out this site: https://pirlwww.lpl.arizona.edu/wiki/MacDesktopProblems#Firefox_Problems

Firefox Problems

Disappearing Bookmarks

If Firefox crashes, you may appear to lose your bookmarks. Starting with Firefox 3, automatic backups of your bookmarks are created automatically, so one fix is to try to restore from a recent automatic backup. To do this, select the Organize Bookmarks... item from the Bookmarks menu. Click on the rightmost button near the top of the window that appears and select Restore and pick the date of the backup from which you wish to restore. This should bring back your bookmarks.
If this fails with the message "Unable to process the backup file", the places.sqlite file in your Firefox profile may be corrupt. This file stores the bookmarks and your browsing history, but it may be deleted, as it will be re-created at run time. The bookmarks will be re-created from the bookmarks.html file in your profile, but your browsing history will be lost. To do this:
go to ~/Library/Application Support/Firefox/Profiles (either in the Finder or by using a terminal). There you'll see an oddly-named directory which contains your Firefox user profile. Descend into that directory and find the files named places.sqlit*. You may see places.sqlit, places.sqlite and places.sqlite-journal. With Firefox stopped, move all these files aside (e.g. to your Desktop) or rename them. Then start Firefox again and see if your bookmarks reappear.
Firefox won't start

Sometimes Firefox crashes and you get this message about "A copy of Firefox is already open. ..." when you try to restart. The following "find" command will fix things up so Firefox will restart:
/usr/bin/find ~/Library/Application\ Support/Firefox/Profiles/ -name "\.parentlock" -delete
In fact, you can do a similar thing if Thunderbird crashes on you:
/usr/bin/find ~/Library/Thunderbird/Profiles/ -name "\.parentlock" -delete