New 2kserv won’t allow 2kpro to chat

I have an NT4.0 server that is the main server. I just installed a Win2k server to handle VPN, terminal services, etc… My PROBLEM is that from the new 2K server I can only issue the command “\\computer_name\c$” succesfully to all the NT4.0 workstations except one and not at all to the Win2k Pro workstations. Why would this be? This is a new install of Win2k server and this is the only problem I am having. Terminal services runs fine and so does the VPN as well as other programs.
Thanksin advance, William