If you have problems with current Shockwave Flash plugin versions then check this: see if there are updates for your graphics drive drivers https://support.mozilla.org/kb/upgrade-graphics-drivers-use-hardware-acceleration disable protected mode in the Flash plugin (Flash 11.3+ on Windows Vista and later) https://forums.adobe.com/message/4468493#TemporaryWorkaround disable hardware acceleration in the Flash plugin https://forums.adobe.com/thread/891337 See also: http://kb.mozillazine.org/Flash#Troubleshooting http://kb.mozillazine.org/Error_loading_websites 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 https://support.mozilla.org/en-US/kb/fix-common-audio-and-video-issues?redirectlocale=en-US&redirectslug=Video+or+audio+does+not+play https://support.mozilla.org/en-US/kb/fix-common-audio-and-video-issues