Mantis 1.2.1 LDAP Search Returned false

[warshall.guo]

Guys,

I really need your help.

I am using Mantis 1.2.1 + PHP 5.2.13.
When I try to integrate Mantis with LDAP, i encountered a issue.
Here is my config_inc.php:
=================================================================================================================
$g_login_method = LDAP;
$g_ldap_server = 'ldap://192.168.0.237';
$g_ldap_port = 389;
$g_ldap_root_dn = 'DC=cn,DC=orgname,DC=com';
$g_ldap_organization = '';
$g_ldap_uid_field = 'sAMAccountName';
$g_ldap_realname_field = 'CN';
$g_ldap_bind_dn = 'CN=firstname.lastname,OU=project,OU=dept,OU=orgname,DC=cn,DC=orgname,DC=com';
$g_ldap_bind_passwd = 'H.12345678';
$g_use_ldap_email = OFF;
$g_use_ldap_realname = OFF;
$g_ldap_protocol_version = 3;
$g_ldap_follow_referrals = ON;
$g_ldap_simulation_file_path = '';
=================================================================================================================

Then, when I try to login, the ldap_authentication fails.
==========================================================================================================================
ldap_api.php ->function ldap_authenticate_by_username ->$t_sr = ldap_search( $t_ds, $t_ldap_root_dn, t_search_filter, $t_search_attrs );
==========================================================================================================================

I am sure I already connect to LDAP server, because log tells
====================================================================
2010-07-28 11:52 CST ldap Connection accepted to LDAP server
2010-07-28 11:52 CST ldap Setting LDAP protocol to to ldap server to 3
2010-07-28 11:52 CST ldap Attempting bind to ldap server with username and password
2010-07-28 11:52 CST ldap bind to ldap server successful
=====================================================================

So anyone ever meet this situation?
Really appreciate if your guys can help me out here.
Thank you~