On Systems B (also XP with IE6), trying to access the router witht he same IP address gives me a not-found response. However, ping works. System B was connected wirelessly to System A's router, without problems. Re-enabling the wireless adapter, B rejoins the network with no problem.
On System C (also XP with IE6), the same procedure gives me the same not-found response, and ping fails. System C was also a wireless node, but it never received a solid wireless signal, so access was flakey.
I used the same CAT-5 cable on all three systems, but the NIC's have never been used before on A&B.
What settings or other issues might cause the difference in responses among the three machines?