Firefox 3.6.13 (Mac Mini, OS 10.4.11) has repeatedly been losing my bookmarks in random fashion. For example, all bookmarks in a single folder have disappeared. Randomly, my bookmarks toolbar is truncated to just 6 items, although all toolbar bookmarks remain visible in the Library. The Library will randomly lose the http location for two to four bookmarks and then those "zombie" bookmarks cannot be accessed, deleted, moved, or edited. I've tried Safe Mode, same problem. I've disabled all add-ons in Normal Mode, same problem. I've reverted to bookmark backups and everything is okay for a short time (minutes sometimes, hours others), then the problems reappear on different bookmarks. Totally frustrating and maddening.