Setup of NT4/Windows 2000 Trusts

The W2K domain can map drives to shares on the NT4 PDC. The NT4 network cannot achieve the same to the W2K PDCE. What do we troubleshoot next? What ports and protocols are necessary? The W2K resource kit states, that the Netlogon Service uses RPCover IP, how do you verify RPC’s are working in both directions? The W2K domain keeps getting domain not found when setting up the trust.