Additionl Domain not access to primary domain

Some body help me

There two win 2003 std,one is primary other one is additional domain, Now my problem is I able access from additional domain to promary domain through Ip. Is access. But I am not able to access through name, Is showing Access Denied,If I am test Dns from additional domain Ip to name is resolving but name to ip not able to resolve. What may be the problem.
Please some body help me.
Dharmesh