After updating, there are bugs with the address bar, back button, and tabs
After recently updating, the back button frequently becomes disabled for no reason. If I go to another tab then come back, it fixes itself. Sometimes the address bar becomes stuck and won't update so that the address shown is incorrect. Also, whenever press the X on the first tab to close it, it doesn't do anything. If there are only two tabs and I try to close the first one, the other one closes instead (very annoying!). Also, when the address bar was not behaving, the favourite star disappeared and I had trouble when trying to paste an address into the address bar.
Alla svar (1)
That combination of problems indicates a problem with the file that store bookmarks and history, for details on fixing it see Locked or damaged places.sqlite - MozillaZine Knowledge Base.