NTLM_SSO doesn't authenticate DOMAIN\\user

Dear all

I'm trying to let Active Directory users to login via NTLM and I have some issues.
I'm working on debian 6, moodle 2.3.1+

I already succeeded in doing that on another network, so I've broken my head more than a bit, but then Iñaki came to help.
I'm working now on a different network (different school site) and the AD configuration is different.
If I perform a wbinfo -u I get:

DOMAIN\user1
DOMAIN\user2
DOMAIN\user3

Please, not the /etc/samba/smb.cnf has the "winbind use default domain = Yes" commented

# winbind use default domain = Yes

I did it before after reading some useful post from the forum.

I put a line into /var/www/moodle/auth/ldap/auth.php, to log if the $_SERVER['REMOTE_USER'] was set and the result is:

REMOTE_USER: DOMAIN\\username

And the NTLM authentication fails.

Any advice?

Thanks in advance for your help

Best regards

stefano