Without the LDAP entry you're attempting to authenticate against it
is hard to say. I have gotten Samba to work with LDAP before; however, I
don't currently have it setup as I'm re-structuring my LAN servers at
the moment. Of interest in the LDAP entries is that Samba has it's own
schema of attributes for which it looks for to authenticate and they are
not the same used for POSIX authenticates typically used for PAM & NSS
authentication. It actually maintains two (2) password attributes for
Samba IIRC.