Have you tried this?
To resolve this problem, reinitialize the WDS server after you move the WDS server to a different organizational unit. To do this, follow these steps:
Click Start, click Run, type cmd, and then click OK.
At the command prompt, type wdsutil /uninitialize-server, and then press ENTER.
Move the WDS account to Active Directory in the new organizational unit.
To reinitialize the WDS service, type wdsutil /initialize-server /reminst:{RemoteInstallFolder} at a command prompt, and then press ENTER.
Pulled the data from here.
http://support.microsoft.com/kb/927770
