trust relationship problems

There is a 2 way trust relationship between domain a and domain b on the same lan.
In domain a we have a PDC (wins server) and a BDC.
In domain b we have only a PDC.
This trust relationship is good set.
But the problem is that the access is onlyworking one way.
When I am connected to a PC in domain a, and want to access a pc in domain b, it work fine.
But when I am connected to a PC in domain b, and want to access a pc in domain a, it do not work.