Try checking to see if your copy of Java or Flash is up to date and working correctly. On firefox you can do this by going to the Firefox Plug-In Check, at http://www.mozilla.org/en-US/plugincheck/

You can check for problems caused by a recent Flash 11.3 update and possibly downgrade to Flash 11.2 or 10.3. *https://support.mozilla.org/kb/flash-113-doesnt-load-video-firefox *https://support.mozilla.org/kb/flash-113-crashes ---- Try to disable hardware acceleration in Firefox. *Tools > Options > Advanced > General > Browsing: "Use hardware acceleration when available" *https://hacks.mozilla.org/2010/09/hardware-acceleration/ *https://support.mozilla.org/kb/how-do-i-upgrade-my-graphics-drivers ---- Try to "disable the hardware acceleration" in the Flash Player. *http://helpx.adobe.com/flash-player/kb/video-playback-issues.html See also: *https://support.mozilla.org/kb/keep-flash-up-to-date-and-troubleshoot-problems Flash "Display settings" window: *http://www.macromedia.com/support/documentation/en/flashplayer/help/help01.html