Try to Wait a bit longer before reopening Firefox to give Firefox more time to close completely. Use "Firefox/File > Exit" (Mac: "Firefox > Quit"; Linux: "File > Quit") to close Firefox if you are currently doing that by clicking the close X on the title bar. See "Hang at exit": *http://kb.mozillazine.org/Firefox_hangs See "Firefox hangs when you quit it": *https://support.mozilla.com/kb/Firefox+hangs