Saw a few Firefox installation problems in other messages so decided to try it. Went to FIrefox, said “Check for Updates”. Got a notice there was one, so checked “Install It”. The Firefox installer went to work, and soon I got a popup saying Firefox wanted to do something. Selected OK, Act as Installer Updater, said yes to installation mode; next I saw was Firefox restarting to incorporate the new features, and everything was fine. Reason for posting is: Do we really understand the installation procedure for new programs? Is there a problem with installing under both Vista and XP or just under XP? What other problems do you have that might be related to the problem? How to update Comodo and the rules to alleviate the problems? I have installed a few other small upgrades also, and had similar results-no stopping in the middle, no strange behavior, … And would like to learn how to keep it that way. 
Hello sded
Just tried it a few minutes ago myself. Worked like a charm. Total of 3 popups, two of which were for CAVS to approve Firefox.
John