domain admin accessing domain controller

A real issue with accessing a domain controller (Win2000) from an NT server (not domain controller). Access was ok prior to the W2k system becoming a DC. The NT user (member of all domain groups is able to access a W2k3 DC, but not the W2k0 DC. When trying, the notice says “You do not have appropriate rights for this server.” Can’t get into the W2k0 local users and groups add-in as Active Directory is controlling this. In AD, the user has all the respective rights. Can anyone provide any suggestions as to where to look? This is becoming quite frustrating.