Running Windows 7 with all updates. Starting with Firefox version 29.0.1, Firefox frequently hangs when I exit. When restarting Firefox, I get "Firefox is already running, but is not responding...". I then have to manually stop firefox.exe*32 before I can restart the program. I have applied all the suggested fixes (disable all add-ons, extension, and themes), and made sure I can delete the parent.lock file. Also noted the shut down delay mentioned with the Vista user. I have the error message occur many minutes after exiting Firefox, although I have often used the X key in the top right screen to exit Firefox consistently with no problems in the past. Has the function of this key changed too? Anyway, I am using the exit key in the pull-down menu now, but still have the hang problem.