Map drive in MS Vista

Hi. I have a NT domain with NT, W2K, W2K3 servers.
Log in as domain admin in Vista PC. On Vista Business 6.0.6000 x64-based I can map a share from a NT server, but not from Win2K, WinXP or Win2K3. I have ping from the server,”Client for Microsoft networks” is installed. For command “net view \\server2k3”, I receive “System error 5 has occurred. Access is denied”. This is a domain admin account, works fine when I am on XP, map is ok for NT shares. Just W2K, W2K3 and XP shares can’t be mapped from this Vista. How to make a map ?