Use one of these to close Firefox if you are currently doing that by clicking the close X on the Firefox title bar.

• "3-bar" menu button > Exit (Power button)
• Windows: File > Exit
• Mac: Firefox > Quit Firefox
• Linux: File > Quit

See also:

• https://support.mozilla.org/kb/Firefox+is+already+running+but+is+not+responding
• http://kb.mozillazine.org/Profile_in_use

Quit Firefox {web link} Quit Firefox provides statusbar and Toolbar buttons to quickly shut down Firefox. It is especially useful for laptop users.

cor-el said

Use one of these to close Firefox if you are currently doing that by clicking the close X on the Firefox title bar.

• "3-bar" menu button > Exit (Power button)
• Windows: File > Exit
• Mac: Firefox > Quit Firefox
• Linux: File > Quit

See also:

• https://support.mozilla.org/kb/Firefox+is+already+running+but+is+not+responding
• http://kb.mozillazine.org/Profile_in_use

Of course all of these methods 'close' Firefox, but the next time you try to start Firerfox, you find out that it's still running from previous close. And my profile is marked Read Only, and I change that, save, but profile still shows read only. Perhaps if this could be permanently changed, that might solve the problem.

I installed 'Quit Firefox' but see nothing different on the screen, no toolbar, no additional icons, nothing. Website for the author no longer in existence. Yes, in the tools menu, it does show that it is installed. Too bad, I would really like to solve the problem.

https://support.mozilla.org/en-US/kb/how-to-fix-preferences-wont-save

Note: Some software, like Advanced SystemCare with Surfing Protection, can protect files in the Firefox profile folder against changes. If you have such software then check the settings or uninstall this software.

https://support.mozilla.org/en-US/kb/firefox-hangs-or-not-responding

https://support.mozilla.org/kb/Firefox+is+already+running+but+is+not+responding

Type about:customizing<enter> in the address bar. In the new window, look for the icon. When you find it, hold down the left button on it, and move it to where you want it to be. You can move any of the icons you want from here, but some icons are locked in place.

There is also a Restore Defaults button at the bottom middle.

I now have the icon. THANK YOU. but ongoing problem not solved. Firefox is still not fully closing and when re-opening Firefox again, I get a message that it is still running. I again note that Windows Problem Reporting runs immediately on the attempted close of Firefox. Something not right and it happened with vrsn 46 installation.

Used info form the suggested reading and started Firefox in protected mode. Firefox reliably shut down without problems. I copied my profile (to desktop), uninstalled Firefox completely, verified removal of all Mozilla Firefox files, restarted computer, installed new X64 version of Firefox, copied my bookmarks file from previous profile into the new X64 Mozilla Firefox profile. Everything works as it should. No hang on exit and exit is very quick.

Thanks for all the suggestions.

That was very good work. Well Done.