Sounds like the network properties are screwed up. I’m guessing either a gateway is configured when you don’t have one, you’ve got a proxy server defined, or your DNS addresses point to a machine you can’t access from where you are at now.
Make sure the machines are set to receive an IP address automatically and that there are no gateways configured under TCP/IP properties. Once you are connected, go to a dos prompt (command prompt in XP) and type “ipconfig /all” and make sure that it has a configuration for the DNS servers. Try pinging one of the DNS servers. For example, if one of the DNS servers has an IP address of 192.168.0.1 (which it won’t, but there will be 4 numbers) then type “ping 192.168.0.1” and see if it gets a response or if it times out. If it gets a response it will tell you the turnaround time in milliseconds.