Did you try to reboot the computer? Try to disable hardware acceleration in Firefox. *Tools > Options > Advanced > General > Browsing: "Use hardware acceleration when available" *https://support.mozilla.org/kb/Troubleshooting+extensions+and+themes *https://hacks.mozilla.org/2010/09/hardware-acceleration/ ----- Try a clean reinstall and delete the Firefox program folder before reinstalling a fresh copy of Firefox. Download a fresh Firefox copy and save the file to the desktop. *Firefox 18.0.x: http://www.mozilla.org/en-US/firefox/all.html Uninstall your current Firefox version, if possible, to cleanup the Windows registry and settings in security software. *Do NOT remove personal data when you uninstall your current Firefox version, because all profile folders will be removed and you will also lose your personal data like bookmarks and passwords from profiles of other Firefox versions. 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. *(32 bit Windows) C:\Program Files\Mozilla Firefox\ *(64 bit Windows) C:\Program Files (x86)\Mozilla Firefox\ *http://kb.mozillazine.org/Uninstalling_Firefox Your bookmarks and other profile data are stored in the Firefox Profile Folder and won't be affected by an uninstall and (re)install, but make sure that "remove personal data" is NOT selected when you uninstall Firefox. If you keep having problems then also create a new profile. ---- *http://kb.mozillazine.org/Profile_folder_-_Firefox *http://kb.mozillazine.org/Profile_backup *http://kb.mozillazine.org/Standard_diagnostic_-_Firefox#Clean_reinstall

Yes, I have rebooted several times. Just now I unchecked the Hardware acceleration item you described. I think I will see if that helps me out before I undertake the un-install process. Thank you very much for this quick and detailed reply.