Start Firefox in <u>[[Safe Mode|Safe Mode]]</u> to check if one of the extensions ("3-bar" menu button or Tools -> Add-ons -> Extensions) or if hardware acceleration is causing the problem. *Switch to the DEFAULT theme: "3-bar" menu button or Tools -> Add-ons -> Appearance *Do NOT click the "Refresh Firefox" button on the Safe Mode start window *https://support.mozilla.org/kb/Safe+Mode *https://support.mozilla.org/kb/Troubleshooting+extensions+and+themes Can you open the about:preferences page via the location/address bar? ---- The System Details List shows that you have multiple Flash plugins. #Shockwave Flash 19.0 r0 #Shockwave Flash 21.0 r0 #Shockwave Flash 22.0 r0 You can find the installation path of all plugins on the <b>about:plugins</b> page. *http://kb.mozillazine.org/Issues_related_to_plugins#Identifying_installed_plugins You can check the Flash player installation folder for multiple Flash player plugins and remove older version(s) of the plugin (NPSWF32) and possibly (re)install the latest Flash player. *(32 bit Windows) C:\Windows\System32\Macromed\Flash\ *(64 bit Windows) C:\Windows\SysWOW64\Macromed\Flash\