AD : Windows cannot verify that the user name is unique

[theeldergeek]

I am trying to add a user to AD and I get the following error message:

Windows cannot verify that the user name is unique because the following error occurred while contacting the global catalog: The server is not operational. Windows will create this user account, but the user can log on only after the user name is verified to be unique. Make sure the global catalog is available. For more information about troubleshooting this issue, see Windows Help.

Advice welcome!

[powdarrmonkey]

Fix your global catalogue; you must have at least one reachable at all times.

[theeldergeek]

Fix your global catalogue; you must have at least one reachable at all times.

A bit over my head, and passed to the man who can, but thanks