hi,
Windows 2003 doesn't allow a search to the root DN.

If i try a search from root DN, I have an 'Operations error' message from php ldap.

To fix this problem, i suggest to add a line like:
ldap_set_option($ad, LDAP_OPT_REFERRALS, 0);
near the line 250 in eZLDAPUser::loginUser (maybe do this fix too in 'cronjobs/ldapusermanage.php')
after
ldap_set_option( $ds, LDAP_OPT_SIZELIMIT, 1000 );
ldap_set_option( $ds, LDAP_OPT_TIMELIMIT, 0 );

And I suggest another things!
add in ldap.ini some settings variable for each ldap_set_option i.e: LDAP_OPT_REFERRALS, LDAP_OPT_SIZELIMIT, LDAP_OPT_TIMELIMIT )