What is your computer system and Firefox? Do you have the Firefox icon on your quick launch? '''Close Firefox.''' Right click on the icon and select '''Open New Tab.''' Sometimes this works. If it opens, close it by '''Menu > File > Exit.''' ------------------ This is not a cure but will make it easier if Firefox locks up in Windows. '''https://support.mozilla.org/questions/997866''' {web link} ----------- '''https://support.mozilla.org/en-US/kb/websites-look-wrong-or-appear-differently''' '''https://support.mozilla.org/en-US/kb/firefox-slow-how-make-it-faster''' '''https://support.mozilla.org/en-US/kb/firefox-uses-too-many-cpu-resources-how-fix''' '''https://support.mozilla.org/en-US/kb/firefox-hangs-or-not-responding'''

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