WIn2003Server doesn’t see one workstation

Hi,
I have a problem with Windows 2003 Server domain controller. I am managing this server remotely. One workstation can log on to domain and everything works fine, however when trying to ping,remote desktop, access shares or anything really from the server it won’t work.
Server doesn’t recognize this machine in the network at all. No problems with any other workstations.
Server is running as dc,dns, file server and Routing/VPN to allow internet access from workstations.

I would appreciate any help.