[horde] problem module in passwd module with ldap

[emacias@usb.ve]

Hi, i'm using passwd module with ldap backend but, i have problem when  
change password user, mi configuration backend is:

$backends['ldap'] = array(
     'name' => 'LDAP Server',
     'preferred' => 'usb.ve',
     'password policy' => array(
         'minLength' => 5,
         'maxLength' => 16,
         'minAlphaNum' => 1,
         'minAlpha' => 2
     ),
     'driver' => 'ldap',
     'params' => array(
         'host' => 'ldap-master.usb.ve',
         'port' => 389,
         'basedn' => 'ou=People,dc=usb,dc=ve',
         'uid' => 'uid',
         // this will be appended to the username when looking for the userdn.
          'realm' => '',
          'encryption' => 'md5',
         // Sure the host == cn in the server certificate
         'tls' => false
     )
);

but show error:  Failure in changing password on LDAP Server:  
Insufficient access

in /horde/config/hooks.php is a function:
  if (!function_exists('_passwd_hook_userdn')) {
      function _passwd_hook_userdn($auth)
      {
          return 'uid=' . $auth . ',ou=People,dc=usb,dc=ve';
      }
  }

I don't know where is the problem?