My machine, "Machine A", is directly connected to the router and works fine. I can open and close ports (servers) as expected on the firewall.
Machines B and C, connected to a linksys switch in the other room and then to the USR8200, will not open ports.
I've even tried designating either of the machines as a DMZ and it still won't open the f-in port. I've turned off XP's firewall. There's no third party firewall. Nothing that I can tell. The two computers always remain shut. The only difference is that my machine is connected directly with the lan cable and the others go through the linksys. It's simply a switch though, and I wouldn't imagine it to be causing anything.