I have tried several times to upgrade from FF 3.6.13 to the latest version, and am still being prompted to do so. Apparently, my iMac OSX version 10.5.8 doesn't have enough capacity for the upgrade. Lately, I have had a few crashes when trying to access my E-mail. Could the crashes be related to the failure to upgrade ? If I am unable to upgrade, I may have to switch to Safari which, I expect, would be more Mac friendly.