I am having the same problems and your website is not even letting me use the 'send updates' page for a request on solving this problem.

The updater wasn't able to update all the files and some were left as older versions. Do a clean reinstall. See: [http://kb.mozillazine.org/Browser_will_not_start_up#XULRunner_error_after_an_update Browser will not start up - XUL Runner error after an update] #Download a fresh Firefox copy and save the file to the desktop. #*Firefox 6.0.x: http://www.mozilla.com/en-US/firefox/all.html #Uninstall your current Firefox version. #*'''''Do not remove personal data when you uninstall the current version''''' #*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. #*See [http://support.mozilla.com/en-US/kb/uninstalling+Firefox Uninstalling Firefox] '''''and''''' [http://kb.mozillazine.org/Uninstalling_firefox Uninstalling Firefox (Mozillazine)] #*Also see: [http://support.mozilla.com/en-US/kb/Backing+up+your+information Backing up your information] '''''and''''' [http://kb.mozillazine.org/Profile_backup Profile backup (Mozillazine)] #Remove the Firefox program folder before installing that newly downloaded copy of the Firefox installer. #*It is important to delete the Firefox program folder/directory to remove all the files and make sure that there are no problems with files that were leftover after uninstalling. #*See: http://kb.mozillazine.org/Installation_directory #Install the fresh copy of Firefox that you downloaded in step 1 '''If this reply solves your problem, please click "Solved It" next to this reply when <u>signed-in</u> to the forum.'''

Are you using ZoneAlarm Extreme? I've seen this issue a lot of times reported as caused by the virtualization that is used by ZAE.