samba - Jun 2007 - client 2 client access

Hello, 
 
I use 3.0.25 samba server as PDC. I have installed samba server, 2 work
stations joined into domain. Ping between server and clients are good, and
between client good too.
 
But when I try to access from client A to client B, windows' explorer are
hang up. At this time tcpdump show a lot of packets from client B to server,
and samba's log file for machine b say that user auth was passed. It say
very much time:
 
I check machine for viruses, and can't find it.
 
Can you help me?
 
Thanks,
Gennady.