Try to disable hardware acceleration in Firefox (you need to close and restart Firefox). *Tools > Options > Advanced > General > Browsing: "Use hardware acceleration when available" *https://support.mozilla.org/kb/Troubleshooting+extensions+and+themes You can check for problems with current Shockwave Flash plugin versions and try this: *disable protected mode in the Flash plugin (Flash 11.3+ on Windows Vista and later) *disable hardware acceleration in the Flash plugin See also: *http://kb.mozillazine.org/Flash#Troubleshooting