join NT Server 4.0 in 2003 native mode

Hi,

I have a Windos NT server 4.0 in a NT domain. Is not a BDC or PDC. Qe
are consolidating all domains in a 2003 R2 Native mode. I'm trying to join
the NT server 4.0 from the old domain (NT domain) to the 2003 R2 domain and
we have an error "Is not posible to contact with the domain controller". I
ping the both domain from the NT Server. We have relationship between the
both domains.

Any help will be appreciated.

Thanks