Did you try to reboot the computer since this happens? Start Firefox in <u>[[Safe Mode|Safe Mode]]</u> to check if one of the extensions (Firefox/Tools > Add-ons > Extensions) or if hardware acceleration is causing the problem. *Switch to the DEFAULT theme: Firefox/Tools > Add-ons > Appearance *Do NOT click the Reset button on the Safe Mode start window *https://support.mozilla.org/kb/Safe+Mode *https://support.mozilla.org/kb/Troubleshooting+extensions+and+themes ----- This can be caused by a problem with the key3.db file. You can make a backup copy of the current logins.json and key3.db files in the profile folder just to be sure before proceeding. You can use this button to go to the current Firefox profile folder: *Help > Troubleshooting Information > Profile Directory: Show Folder (Linux: Open Directory; Mac: Show in Finder) *http://kb.mozillazine.org/Profile_folder_-_Firefox You can try to restore a previous version of the key3.db file and possibly the logins.json file. *Right-click: Properties > Previous Versions *http://windows.microsoft.com/en-US/windows7/Previous-versions-of-files-frequently-asked-questions