Strange issue with validation libraries

[eluser]daweb[/eluser]
Hi guys,

I'm running (on line) PHP 5.2.2

In my localhost, instead, 5.1.x

I have this controller:

Code:

class Login extends Controller {

    function __construct()
    {
        parent::Controller();      
        $this->load->library('validation');
        // I HAVE TO ADD THIS LINE TO MAKE VALIDATION WORKING, BUT JUST ONLINE!! //
        $this->load->model('settings_model', 'set');
        // THIS IS A SIMPLE MODEL WITH QUERIES TO DATABASE, THAT'S IT!! //
    }

    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);
    }
} // END Front

Ok! On line and just on line, I had to add $this->load->model('settings_model', 'set') or $this->validation doens't work: it doens't return error array.

Why????