samba - Dec 2007 - password authentication stops but can be restarted

I have several Sun Solaris systems that share directories via SAMBA. After
some period (I think 30 days, which the password expiration period) the
authentication stops with the following messages (all names changed to protect
the guilty):

li_rpc_pipe_open_schannel: failed to get schannel session key from server
W3K_SERVER for domain DOMAINX.
connect_to_domain_password_server: unable to open the domain client session to
machine W3K_SERVER. Error was : NT_STATUS_ACCESS_DENIED.

After successfully running the 'net join' command every thing works fine
for
another 30 days. 

My smb.conf and smb.users are:

smb.conf
[global]
	security = domain
	workgroup = DOMAINX
	netbios name = sun-system-y
	password server = W3K_SERVER
	domain master = no
	local master = no
	preferred master = no

	username map = /etc/sfw/smb.users

[homes]
	writeable = yes
	valid users = +sysadmin
	wide links = no

[app]
	path = /var/data_path
	writeable = yes
	valid users = app_id
	wide links = no

smb.users
id_1 = DOMAINX\win_id_1
id_2 = DOMAINX\win_id_2
app_id = DOMAINX\win_id_app

Note that the Windows password server is Win3K and that I have various
versions of Sun supplied SAMBA. I do have some SAMBA share that use Win2K
authentication and those do not seem to have this issue.