I've the same problem:
When the Win2k PC tries to access the network (My Network Places) the operation times out and a "Workgroup is not accessible. The list of servers for this workgroup is not currently available." window pops up.
So basically it comes down to that the network functions fine (Internet sharing), but that the Win2k PC can't access the network, i.e. see the other PC's on the network or play LAN-games.
I haven't found a solution for this problem yet.