DFS domain root permissions

Setup

Trust relationship setup between Domain A & Domain B. Domain A has multiple domain root DFS shares

Domain admin A can log on to DC in Domain B

Cannot map DFS root \\domain.a\root or \\domain.a\root\share

Configuration information could not be read from the domain controller, either because the machine is unavailable, or access has been denied.

But can map the share \\serv1.domain.a\share

I have checked out http://support.microsoft.com/kb/975440 Running dfsutil.exe /spcinfo from Doman B return the expected results for the available namespaces and servers

I believe this may be a a permissions issue with computer accounts across the domain trust?