Forest to Forest Trusts

I have a Win2003 Forest to Forest Trust (Forest A and Forest B) 2 way-trsnsitive. Forest B has several child domains. I’ve added a Win2000 server to Forest A and I’m attempting to add users from a child domain in forest B to the local administrator group of the new Win2000 server but the domain is NOT visible in the Manage – Local Users and Groups – utility…
I can see the Forest B root domain but none of the child domains – validating the Forest A to B trust works with no errors, I’m really stumpt, help!