samba - Oct 2004 - User authentication on XP workstations from remote Domain

Dear All,
I have a problem with authentication on XP workstaions from trusted domain. 
I have two domains:
domaina   servera                     trusting domain

domainb   serverb                     trusted domain

When I try to logon the user from domainb on XP workstation(in domaina) it gave
me a fail but when I write on servera:

smbclient -L servera -W DOMAINB -U user

the authenticaton is succeded and after then I authenticate user on XP
workstations to. I thing that is the problem in creating unix account on
servera for user from domainb.

Thank you, Sopik Bronislav