Which security software (firewall, anti-virus) do you have? Do you have security software like ZoneAlarm or Avast that has virtualization or sandbox features?<br /> In that case you need to disable that feature and do a clean install of the latest Firefox update. ---- Download a fresh Firefox copy and save the file to the desktop. *Firefox 9.0.x: http://www.mozilla.org/en-US/firefox/all.html Uninstall your current Firefox version, if possible. *Do NOT remove personal data when you uninstall the current version or you lose your bookmarks and other data in the profile folder. Remove the Firefox program folder before installing that newly downloaded copy of the Firefox installer. *It is important to delete the Firefox program folder to remove all the files and make sure that there are no problems with files that were leftover after uninstalling. *http://kb.mozillazine.org/Uninstalling_Firefox Your bookmarks and other profile data are stored elsewhere in the Firefox Profile Folder and won't be affected by a reinstall, but make sure that you do not select to remove personal data if you uninstall Firefox. ---- *http://kb.mozillazine.org/Profile_folder_-_Firefox *http://kb.mozillazine.org/Profile_backup *http://kb.mozillazine.org/Standard_diagnostic_-_Firefox#Clean_reinstall