This happened to me more then two times. Say you installed brand new Windows Server 2008 (R2) domain controller and you start to have some mysterious problems. Other day I was trying to demote last Windows Server 2003 DC in Lab with presence of W2K8 DCs. I get this error message:
"The specified domain either does not exist or could not be contacted."
It turn out to be SYSVOL share is missing in new Windows Server 2008 DCs. Why it happens every time I install new W2K8 DCs.
Anyways this MSKB-947022 helped me every time: The NETLOGON share is not present after you install Active Directory Domain Services on a new full or read-only Windows Server 2008-based domain controller