I have an existing domain 2003, with 3 AD controllers, and 2 2000 servers. I upgraded both 2000 servers to 2003 OS. But on one of the servers I am getting authenticating errors, can't fine user accounts to add to shares, etc. I tried to add a domain controller role to the server but am unable to due to a dns error. I can ping and resolve all addresses formain dns name of domain, but am unable to nslookup: domain unknown. All other servers in domain work fine. Is there an additional test or resolution in order to get this server onto the domain correctly? I can view all network shares, etc. But the underlying dns resolution is a problem that keeps creeping up. Sometimes it is no machine account in the domain, others it is no authentication.