Clear the cache and the cookies from sites that cause problems.<br /> Also make sure that you aren't blocking cookies in Firefox and that local storage in the Flash player in enabled (right-click -> Global Settings). "Clear the Cache": *Tools > Options > Advanced > Network > Offline Storage (Cache): "Clear Now" "Remove Cookies" from sites causing problems: *Tools > Options > Privacy > Cookies: "Show Cookies" Start Firefox in <u>[[Safe Mode]]</u> to check if one of the extensions or if hardware acceleration is causing the problem (switch to the DEFAULT theme: Firefox/Tools > Add-ons > Appearance/Themes). *Don't make any changes on the Safe mode start window. *https://support.mozilla.org/kb/Safe+Mode See also: *http://kb.mozillazine.org/Resetting_preferences *https://support.mozilla.org/kb/Resetting+preferences