[Samba] Cannot find Domain Master Broswer

[Gianluca Culot]

After upgrading my freebsd 6 box to samba-3.0.26a_2,1 
I get this error 
Dec 12 10:16:58 mail nmbd[10450]:   find_domain_master_name_query_fail:
Dec 12 10:16:58 mail nmbd[10450]:   Unable to find the Domain Master Browser
name DMSWARE<1b> for the workgroup DMSWARE.
Dec 12 10:16:58 mail nmbd[10450]:   Unable to sync browse lists in this
workgroup.

the DMSWARE domain is the local domain, and no other server is blaiming.
 
any clue about the problem origin ?
the samba is behind a firewall, so no broadcast is possible, and I do not
have a wins server.
 
net ads testjoin 
reports : Join is OK
 
net rpc testjoin 
reports : Unable to find a suitable server
Join to domain 'DMSWARE' is not valid

Any hint ?