How can I repair “Windows cannot connect to the domain”?

If the client does not log in within 30 seconds, they receive the following message:
“Windows cannot connect to the domain, either because the domain controller is down or otherwise unavailable, or because your computer account was not found.”

The service is running Windows 2008 SP1

The client is running Windows XP Pro.

I have set the screensaver delay for 5 minutes in the registry of the server, and also tried changing the client computer from “domain” to “workgroup” to no avail.

Any help would be appreciated.

TIA

James