If there are problems with updating or with the permissions then easiest is to download the full version and trash the currently installed version to do a clean install of the new version.

Download a new copy of the Firefox program and save the disk image (dmg) file to the desktop

• Firefox 7.0.x: http://www.mozilla.com/en-US/firefox/all.html

• Trash the current Firefox application to do a clean (re-)install
• Install the new version that you have downloaded

Your profile data is stored elsewhere in the Firefox Profile Folder, so you won't lose your bookmarks and other personal data if you uninstall and (re)install Firefox.

• http://kb.mozillazine.org/Profile_folder_-_Firefox

Thanks for your assistance. I downloaded the updated version (7.0.1 dmg) as instructed, but I cannot delete the original. When I attempt to put the icon square in the trash or delete it, a message tells me it is in use. However, Firefox has been removed from the Applications folder and no window is open. As far as Permissions are concerned, the Info box tells me I can "read only." Whether that is relevant or not is beyond me, especially since I am the sole user of the Mac Post Script After traveling a lot of back roads, I did manage to erase the previous version of Firefox and install the updated version. Although I couldn't duplicate the journey or advise anyone on how I did it, the system is now working fine. Thanks again.