My new linksys router was about to go back to frys when I discovered that OS X has a network setting called “DHCP plus manual address” in which you can specify just the IP address that you want, but get all the rest of the info from the DHCP. It seems like a violation of DHCP, but it fixes the problem with the linksys router in that it doesn’t let you do static MAC to IP allocation.
To get ichatAV working, forward UDP port 5060 and ports 16384-16403. Ideally, I’d like to get the port triggering setup to work, so that if someone else wants to use it behind the firewall, it’ll work.