Did nothing different, but started FF again and the update was successful. This is after over a dozen attempts. Automatic update fails, but gives no reason. Tried a Manual update (Firefox Setup 31.0.exe) and it doesn't run??? Tried running in administrator mode and nothing seems to happen (???).. When I click on '?' (help) / about and the Applying update... message just keeps rotating and rotating for a LONG time, then prompted to restart. I do and get error message the partial update could not be applied...that it will try a complete Update. It loads and runs the complete update, and then displays an endless "Applying update" message. After several minutes of nothing happening, I x'd out and am still on release 30, with the message to restart again. Running Windows 8.1 As of today, Firefox continues to fail upgrading to version 31. I'm going to try manually disabling all my add-ons and see if this helps. Well, this didn't work. Tried running FF in 'safe mode' ... this also didn't work. I did notice that when asked to "restart FF", the tabs looked a little weird ... boxy is the only way to describe it. The upper right side minimize, exit window icons were also "cut in half". Very weird. Another problem. In my download directory I now have three executables that I CANNOT DELETE. Says they are in use by some other program. Looked at all running processes and did not seed anything FF-related running. Tried rebooting PC, did not run FF, and still can't delete Firefox Setup 31.0.exe Firefox Setup Stub 31.0.exe Firefox_Setup_31.0.exe (this setup program was downloaded from cnet.) As of now I'm using Chrome since I don't know what's going on with FF. I'll check back daily to see if there's a solution. I haven't tried uninstalling FF and then re-installing. I understand that I should be able to save all my settings, so I might try this in a week if I don't see a solution.