I just updated to Firefox 36.0, and I have the same problem as http://support.mozilla.org/en-US/questions/1036130 , although in addition to that I've lost my search engines and tiles. As far as I know this problem didn't occur until after I'd updated and then quit Firefox and opened it again later. But I could be wrong; in fact, before I noticed this problem, I did notice I couldn't save bookmarks. This is still the case. I still have all my extensions, settings, passwords, etc. As far as I know the only things affected are bookmarks, history (including download history), tiles, and search engines. They're just empty. Restarting does not change anything. In fact, it doesn't even have my history from the last session since the problem started! It's like it's just not saving anything at all. Update: It's come to my attention that while the back button works, I cannot pull down the history in it, and the forward button never appears at all. It's like it's literally just not saving a single thing. I checked my profile: The places.sqlite file is there, and there is a bookmarkbackups folder; the search.sqlite file is not there, but the searchplugins folder is; there is no sessionstore.js file, but there is a sessionstore-backups folder with the files previous.js, recovery.bak, recovery.js, and several upgrade.js files; formhistory.sqlite is there.