When I start mozilla firefox web browser, sometimes I see a message saying that "a Mozilla Firefox is already running, please close it or restart your program", while I don't have one running at that time. What is the problem?

Question

When I start mozilla firefox web browser, sometimes I see a message saying that "a Mozilla Firefox is already running, please close it or restart your system". As a matter of fact, there is no firefox browser running at that time. Since I cannot do anything about it, I have to restart my computer before I can use the web browser, which bothers me dearly. What is the problem?

Answer 1

Plug-in and tasks started by Firefox may continue after attempting to close Firefox. The "X" in the upper right-hand corner closes the Window (same as Ctrl+Shift+W) but even if it is the last Firefox window, it does not necessarily close Firefox .
'''The only proper way to exit Firefox is to use Exit through the File menu''', not the "X" in the upper right corner of last Firefox window.
''Menus hidden: then use Alt+F then X.''
'''Firefox hangs''' | Troubleshooting | Firefox Support ''(some extensions cause a problem)''
* http://support.mozilla.com/kb/Firefox%20hangs#w_hang-at-exit
Use the '''Windows Task Manger''' to remove all running firefox.exe in the "Processes"
tab of the Windows Task Manager, then restart Firefox.
"'''Restartless Restart'''" extension for Firefox 4.0 only (2 KB download )
* https://addons.mozilla.org/firefox/addon/249342/
use to close and restart Firefox after enabling or disabling an extension, switching
to a new theme, or modifying configuration files, then you don't have to worry
about delay or have to look in the Task Manager to see if Firefox is closed yet.
Uses keyboard shortcut "'''Ctrl+Alt+R'''" or a file menu option.
'''Windows 7''' users can use '''Ctrl+Shift+Esc''' to get to the Windows Task Manager quicker than starting with Ctrl+Alt+Del.