So, been chasing this one for a couple of hours or so, can't find any solutions and it's happened several times under various conditions. A couple of days ago, I updated firefox and my profile seemed to fail in some way- my history disappeared, my open tabs remained the same in number but lost their associated information(they all became "new tabs"). All the bookmarklets except three visible in my bookmarks toolbar disappeared. I was running extremely low free disk space at the time, and it's possible firefox was unable to write to the profile. I attempted to load bookmarks from the automatic backup, and got a "unable to process backup file" error. I'd made a backup a couple of days before, so I restored the profile from that date and all went perfectly. I browsed for a bit, then shut down(firefox) and relaunched. My history and tabs had remained from before the shutdown/relaunch(including the browsing I'd done), but the bookmarks had returned to their former state- three bookmarks remained, the first three visible in the bookmarks toolbar. I added another bookmark, and restarted the browser- the bookmark had disappeared. Everything else remained the same. using the same install of firefox on a blank profile lets me add bookmarks that persist over restarts. I went through support.mozzila.org and checked the troubleshooting I could find- the places.sqlite file has the right permisions, is unlocked, etc. Bookmark backups will not load. Options in about.config cannot be edited. Trying to edit them will result in the edit box appearing, being able to change the value, and being able to submit the change, however the value does not change and no error shows.