Getting VirusScan through a firewall

I am running NAI’s VirusScan Enterprise 7.1 and a Kerio Firewall on a Windows 2000 server. With the firewall running, my virus updates can’t connect to the NAI server. With the firewall disabled, they do. I have created a firewall rule that enables traffic in both directions on ports 20, 21, and 80 when MCUPDATE.EXE is executed (which is what NAI said to do). But it doesn’t work. I also have an FTP server running successfully on the same server. So I tried duplicating it’s firewall rule for VirusScan. But again, no luck. Any ideas on how to resolve this?