You can use the SearchReset extension to reset some preferences to the default values. *https://addons.mozilla.org/firefox/addon/searchreset/ Note that the SearchReset extension only runs once and then uninstalls automatically, so it won't show on the "Firefox > Add-ons" page (about:addons). If you do not keep changes after a restart or otherwise have problems with preferences, see: *http://kb.mozillazine.org/Preferences_not_saved ----- Note that your System Details List shows multiple Flash plugins. *Shockwave Flash 14.0 r0 *Shockwave Flash 11.6 r602 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\