[Samba] Winbind errors result in no logins!

[Trimble, Ronald D]

Everyone,
                We are currently seeing a very strange problem on our server.  Everything will be running along smoothly and then all of a sudden, nobody will be able to login.  Looking through the logs reveals the following messages...

Apr 24 10:55:15 LINUX-1 httpd2-prefork: pam_winbind(httpd): pam_winbind_request: read from socket failed!
Apr 24 10:55:15 LINUX-1 httpd2-prefork: pam_winbind(httpd): internal module error (retval = 3, user = 'NA\nda')
Apr 24 10:55:15 LINUX-1 httpd2-prefork: pam_winbind(httpd): [pamh: 0xa0c91c0] LEAVE: pam_sm_authenticate returning 3
Apr 24 10:55:17 LINUX-1 httpd2-prefork: pam_winbind(httpd): pam_winbind_request: read from socket failed!
Apr 24 10:55:17 LINUX-1 httpd2-prefork: pam_winbind(httpd): internal module error (retval = 3, user = 'na\sja')
Apr 24 10:55:17 LINUX-1 httpd2-prefork: pam_winbind(httpd): [pamh: 0x9c58c68] LEAVE: pam_sm_authenticate returning 3
Apr 24 10:55:31 LINUX-1 httpd2-prefork: pam_winbind(httpd): [pamh: 0x9c58630] ENTER: pam_sm_authenticate (flags: 0x0001)

Also, once the problem begins, the CPU goes to 95%+ for winbind!  The apache2_error log shows errors like this...

[Fri Apr 24 16:08:08 2009] [error] [client 192.xxx.xxx.xxx] PAM: user 'na\\naj' - not authenticated: Error in service module
[Fri Apr 24 16:08:15 2009] [error] [client 172.xxx.xxx.xxx] PAM: user 'na\\sja' - not authenticated: Error in service module
[Fri Apr 24 16:08:29 2009] [error] [client 192.xxx.xxx.xxx] PAM: user 'na\\nda' - not authenticated: Error in service module
[Fri Apr 24 16:09:48 2009] [error] [client 192.xxx.xxx.xxx] PAM: user 'na\\nda' - not authenticated: Error in service module

Restarting the winbind and smb services clears up the problem immediately, but we can't seem to figure out what is going on.  Does anyone have any suggestions of things to try?  Have any of you seen this before?

Thanks,
Ron