Ghys,

Try changing your /etc/smb.conf file as follows:

Change:
ldap admin dn = cn=Administrator,cn=Users,dc=domain,dc=com

To:
ldap admin dn = cn=LDAPQUERYUSER,cn=Users,dc=domain,dc=com

(Where the LDAPQUERYUSER is the Windows user account that you created for making LDAP queries.)

Then issue this command to set the correct password for the ldap query user:

smbpasswd -w <LDAPQUERYUSER's - password>

Then stop /etc/init.d/smb and /etc/init.d/winbind, then restart in same order

Then try su to windows user - (check /var/log/messages)
Then try getent passwd



Shannon