ldap_add() return LDAP_UNWILLING_TO_PERFORM

["MINGHAO WANG, BLOOMBERG/ 499 PARK" <MWANG12@bloomberg.net>]

Hello,
  I am a new bie to ldap. Now I am trying to add a user to Windows 2003 active
directory by using ldap api. After I call ldap_add() and set an attribute
"userAccountControl", the function return an error as LDAP_UNWILLING_TO_PERFORM.
  Does anyone know why? Does the active directory has some limitations on the
user attribute? Here is what I did:
    char *acc_control[] = { "512", NULL }; //trying to enable the user account.
    AccControl.mod_op = LDAP_MOD_ADD;
    AccControl.mod_type = "userAccountControl";
    AccControl.mod_values = acc_control;
    // Build the array of attributes.
    LDAPMod *NewEntry[10];

    NewEntry[0] = &Name;
    ...
    NewEntry[9] = &AccControl;
    NewEntry[10] = NULL;

    //syncronous call
    ret=ldap_add_s( ld, entry_dn, NewEntry);                                    
  The error details is: error=0000052D: SvcErr:DSID-031A0FBC, problem 5003 
(WILL_NOT_PERFORM) data 0
  Thanks a lot.
Sincerely, Howard