[Samba] 3.0.23b domain member not accessible

[dovecot auth]

I portupgraded my samba domain server and domain member to 3.0.23b from
3.0.23 and found that the domain member was not accessible from
workstations.  The error message:

\\HOSTNAME is not accessible.
There are currently no logon servers available to service the logon request.

In the log.winbindd of the domain member, I found:

[2006/08/23 22:52:00, 0] nsswitch/winbindd.c:request_len_recv(517)
  request_len_recv: Invalid request size received: 1840

If I use smbclient to connect to shares on localhost, it will produce
"session setup failed: NT_STATUS_NO_LOGON_SERVERS".

My OS is FreeBSD 6.1, and I did not have this problem with 3.0.23 or earlier
versions.  Please help.

Adam