Pre-router. An 8-port Linksys 10/100 switch, to which was attached: Workstation Pulsar, a P-133 based PC with a D-Link 100baseT NIC. Workstation Voyager, an AMD K6-350MX workstation with a Linksys 100baseT NIC. Voyager also contained a 3Com 100BaseT NIC attached to a cable modem. Both IPX/SPX and TCP/IP installed on both workstations.
Post-router. Pulsar is configured as before, but now connects to the SMC Barricade 4-port router. Voyager is also connected to the router, via the 3Com NIC. And a new workstation, Polaris, an AMD 1600+XP PC is connected via the Linksys NIC.
When I removed the Linksys NIC from Voyager, I also removed all the bindings to that card, and I think I might have just answered my question. I bet I didn't have IPX/SPX bound to the 3Com card, since it wasn't being used for gaming, so I probably removed IPX/SPX entirely, which would prevent the game software from seeing that node, right?