samba - May 2007 - authentication doesn't work when connecting from XP via hostname

We have problems with connecting from some xp pcs to our linux fileserver when
using the netbios name of the server,
when i try to connect the authentication error message apears and asks for user
/password,
the problem occurs only when i connect via host names, when i connect via IP it
works well,
i didn't find anything in the logs and the problem occured today after it
worked for a few days,
some other pcs have no problems with it, can anyone help ?
 
We're using samba 3.0.23d with winbind in a 2k3 SP2 domain using kerberos