Recently TEKNIA tried to add a brand new server running Windows Server 2008 to a Windows Server 2003 Active Directory existing Forest and Domain.

We ran through the steps correctly, such as making sure the DNS was correctly configues and pointing to the existing DNS server (Domain Controller) and ran ADPREP tool from the Windows Server 2008 disks.

On 2003 server the DNS is pointing to itself and DCDIAG does not report any issues

When DCPROMO reached the last stage we received the error "The DSA operation is unable to proceed because of a DNS lookup failure"

Action Taken & Resolution:

• We discovered that IPv6 was at the top of the NIC bindings and was incorrectly being used for DNS resolution.
  
• Disabled IPv6 on Windows Server 2008 so that DNS lookup is able to bind to Windows Server 2003 for DNS resolution
• Performed a DCPROMO on Windows Server 2003 and it successfully completed with no errors
• Server is now is a Domain Controller and has passed all tests

NOTE: And remember.. don't uncheck that IPv6 for SBS as it needs to be enabled on SBS 2008. try changing the binding order.