Are you using the same user accounts on both computers? (i.e. same username and password) A lot of times if you have different accounts on each computer, even the matter of just a different password, that could cause a lot of problems. I suggest creating a user account on the Win2k server computer that matches the user name and password of the account on the win2k pro workstation. However, keep in mind that if you keep the default "Users" group on the account, it will NOT be able to log in locally to the server. You have to add the appropriate permission. However, with my servers, if I ever need to log into the server locally or through Terminal Services, I just use the Administrator account.
Also, do me a favor and go to a command prompt on each computer and type in "ipconfig /all" (without the quotes) and tell me what your IP address, subnet mask, and default gateway. On the network, do you have either a router or DHCP server assigning IP addresses, or are you possibly using static IP addresses? This would be good to know.
Hope that helps. Let me know what you find.