Accessing LAN initiates dial-up connection

I truly hope someone has the answer to this issue because it's driving me nuts:

I have 3 PC's in my home network (a pair of Win2K and 1 XP box). One of the Win2k machines is the Internet Connection Sharing machine. Whenever I attempt to access either of the other two PC's from this machine it initiates a dial-up connection and won't let me access the other machines until it completes it. It's almost as if it has to satisfy itself that the PC it's searching for isn't available remotely before it will look for it locally. Neither of the other PC's exhibit this behavior.

Any ideas?

Did you check the on demand dialing in the connection sharing for the machines....this often drives me mad...