DCPROMO forest error Win2003 r1 addiing Win2003 r1

Current DC is Standard edition Win2003 r1; Server adding as an additional DC is the same.

DCPROMO fails with forest error and says run advprep. The error is the same as if you were trying to add a W2003 to a W2k domain.

Since this is not the case, looking for options. Everything is set for a W2003 forest/trusts. Checked DNS working correctly.
Checked reg settings NTDS parameter is 30.

Suggestions?