samba - Nov 2007 - Winbind runs great for a while then dies with "read from socket failed!"

Hello all,

I experienced a same problem with
http://lists.samba.org/archive/samba/2003-January/059073.html

I use following.

Hardware: Dell PowerEdge 2950
OS: Red Hat Enterprise Linux ES4 Update 4
Kernel: 2.6.9-55.0.2.ELsmp
RPM packages are:
samba-3.0.10-1.4E.12.2
samba-common-3.0.10-1.4E.12.2
samba-client-3.0.10-1.4E.12.2
pam_krb5-2.1.8-1
krb5-libs-1.3.4-49
krb5-workstation-1.3.4-49
krb5-devel-1.3.4-49


Samba server is a member server (Security=ADS) of Win2003 R2 Active Directory.
	net ads join is OK.
	'getent passwd' or 'wbinfo -u/g/t' are no problem.
winbind is used for user authentication for dovecot(POP3).

After a while (3months), winbind dies with following message, then
authentication doesn't work.

pam_winbind[PID]: read from socket failed!
pam_winbind[PID]: internal module error (retval = 3, user = `username'
 |
pam_winbind[PID]: write to socket failed!
dovecot(pam_unix)[PID]: check pass; user unknown
dovecot(pam_unix)[PID]: authentication failure; logname= uid=0 euid=0 tty=
ruser= rhost |
out of memory [PID]
pam_winbind[PID]: request failed: No logon servers, PAM error was 4, NT error
was NT_STATUS_NO_LOGON_SERVERS

After restarting the server, there is no trouble.

I want to know ...
	Why this trouble occurred?
	What is the cause?
	How can I reproduce?

Any help is appreciated,
Satoshi