In addition to the subject message, your System event log may contain:
Event Type: Error
Event Source: NetBT
Event ID: 4321
Description: The name "<WorkGroupName> :1d" could not be registered on the Interface with IP address nnn.nnn.nnn.nnn. The machine with the IP address mmm.mmm.mmm.mmm did not allow the name to be claimed by this machine.
This behavior is probably due to a NetBIOS name conflict between the workstation and another workstation with the same NetBIOS name, or a workgroup or domain with the same NetBIOS name as the workstation.
To fix this problem, do one of the following: