domain admin can’t access domain server

NT4 server is running Symantec Corporate Antivirus application and used to put the updates onto a mapped drive off a Win2K server. At that time, the Win2K was not a domain controller. Since the change to a BDC, unable to access the system. System says access denied. Properties say user doesn’t have appropriate rights access. But same user can access this server from other servers and workstations. Only the NT server is unable to access the mapped drive. Is there something I’m missing. Checked all rights access and nothing has changed. But last two updates from Microsoft the system won’t load. No reason given. All this server does is host network printers and antivirus. Appreciate any suggestions.