Unable to Upgrade Comodo 3.x

I am very satisfied with Comodo Internet Security 3.X but when I was prompted for an upgrade; my system is unable to upgrade my Comodo 3.X. to latest version. The following error incurs "Comodo firewall setup wizard ended prematurely because of an error. Your system has not been modified. To install this program at a later time, run set up wizard again" and a popup error "Cannot install COMODO firewall Error: 1603. Fatal error during installation. Would you like to try again? YES or NO" Do you have any suggestions? I am running Windows XP Professional SP3.
