Ran into this long ago when the domain controller was a tempermental NT4 system. The fix was to restart the domain controller service. So, that seems as good a place as any to start.
When trying to add n client machine to my domain a error is returned stating that the domain controller cannot be contacted. When looking in my network places the domain controller is also not visible, you can map n network drive only by entering the IP of the server not the server name. How do I fix this??????