Strange issue with validation libraries

[eluser]daweb[/eluser]
Another no Xwero.

The callback function is a method of my controller.

Code:

<?php
class Login extends Controller {

    function __construct()
    {
        parent::Controller();
        $this->load->helper('form');
        $this->load->helper('security');
        // utente non autorizzato
        $this->authUser = FALSE;          
        $this->load->library('validation');
        $this->load->model('settings_model', 'set');
    }

    function index()
    {
        $data_stack['pageTitle']   = $this->lang->line('titleLogin');
        $this->load->view('admin/custom_validation/logins_validation.php', '', FALSE);
        if($this->validation->run() == TRUE)
        {
            redirect('front', 'location');
            exit();
        }

        $this->load->view('admin/login/index', $data_stack);
    }
    
    function check_login()
    {
      $username = $this->input->post('username');
      $password = dohash($this->input->post('password'));
      if ($this->erkanaauth->try_login(array('username'=>$username, 'password'=>$password)))
      {
        $this->erkanaauth->updateLastVisit();
        return TRUE;
      }
      else
      {
        $this->validation->set_message('check_login', 'Errore, utente e/o password errati');
        return FALSE;
      }
    }
} // END Front
?>