Originally Posted by jeffshih
If you're using a Windows OS, did you check to see if the firefox.exe process was still running in your task manager even though your Firefox browser was completely closed? Every blue moon it crashes on me and when I relaunch the browser, it asks me to pick a user profile. I just cancel out of that, and kill the errant firefox.exe process in my task manager. After that, everything works like normal again.
Yes, this happens on occasion. It blows up but leaves part of itself running. Kill the offending task from the task manager (processes, not running applications) and everything's fine again.