Cross Domain accounts access issue

Hi,

we have just upgraded our third and last domain controller that was running on 2003 to 2008R2 on our A domain. we now have a new domain controller and DNS server. On our B domain we pointed the domain controllers of the B domain to the new DNS server on domain A. now the B domain users have no access to any resources on A domain.

I have checked the DNS configurations and they all seem to be fine to my knowledge. zone transfer is setup between both domains.

can anyone let me know what the issue might be??