problemas al devolver Isvalid de un Zend_Form

[ApipeMc]

Proyecto/application/forms/LoginForm.php

Código PHP:

  class Application_Form_LoginForm extends Zend_Form
{

    public function init()
    {
        $username = new Zend_Form_Element_Text('username');
        $username->setLabel('Username:')
                 ->setRequired(true)
                 ->setAttrib('id', 'username')
                 ->addValidator('NotEmpty', true)
                 ->addValidator('alnum')
                 ->setDecorators(array(
                     array('ViewHelper',
                           array('helper' => 'formText')),
                     array('Label',
                           array('class' => 'label'))
                 ));

        $password = new Zend_Form_Element_Password('password');
        $password->setLabel('Contraseña:')
                 ->setRequired(true)
                 ->setAttrib('id', 'password')
                 ->addValidator('NotEmpty', true)
                 ->setDecorators(array(
                     array('ViewHelper',
                           array('helper' => 'formPassword')),
                     array('Label',
                           array('class' => 'label'))
                 ));

        $submit = new Zend_Form_Element_Submit('Entrar');
        $submit->setAttrib('id', 'submitbutton')
               ->setDecorators(array(
                   array('ViewHelper',
                   array('helper' => 'formSubmit'))
               ));
        
        $this->setMethod('post');
        $this->setAction('security/login');
        $this->addElements(array($username,$password,$submit));
    }
}  
   

Proyecto/application/controllers/IndexController.php

Código PHP:

  class IndexController extends Zend_Controller_Action
{

    public function init()
    {
        /* Initialize action controller here */
    }

    public function indexAction()
    {
        $form = new Application_Form_LoginForm();
        $request = $this->getRequest();
        $form->isValid($request->getPost());
        $this->view->form = $form;
    }
    
}  
   

Proyecto/application/controllers/SecurityController.php

Código PHP:

  class SecurityController extends Zend_Controller_Action
{

    public function init()
    {
        /* Initialize action controller here */
    }

    public function indexAction()
    {
        // action index
    }
      
    public function loginAction()
    {    
        
        $request = $this->getRequest();
        if (!$request->isPost()) {
            return $this->_helper->redirector('index','index');
        }
        
        $form = new Application_Form_LoginForm();
           if(!$form->isValid($request->getPost())):
               $this->view->form = $form;
            return $this->_helper->redirector('index','index');
        endif;
        
        $modelSecurity = new Application_Model_Security();
        
        $username = $this->_getParam('username');
        $password = $this->_getParam('password');
        
        if($modelSecurity->validarUsuario($username, $password)):
            return $this->_helper->redirector(index, user);
        endif;
            
        return $this->_helper->redirector('index','index');
    }
    
    public function logoutAction()
    {
        Zend_Auth::getInstance()->clearIdentity();
        $this->_helper->redirector('index','index'); 
    }
        
}  
   

Proyecto/application/models/Security.php

Código PHP:

  class Application_Model_Security
{
    public function validarUsuario($username, $password) {
        
    $authAdapter = new Zend_Auth_Adapter_DbTable(Zend_Db_Table::getDefaultAdapter());
        $authAdapter->setTableName('users')
                    ->setIdentityColumn('username')
                    ->setCredentialColumn('password');
        $authAdapter->setIdentity($username)
                    ->setCredential($password);
        
        //$select = $authAdapter->getDbSelect ();

        $auth = Zend_Auth::getInstance ();
        $result = $auth->authenticate($authAdapter);
        if($result->isValid()) :
                    
            return true;
            
        endif;
        
        return false;
    }
}  
   

Proyecto/application/views/scrpits/index/index.phml

Código HTML:

<!DOCTYPE html>
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
  <meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
  <title>Proyecto</title>
  <link rel="stylesheet" type="text/css" href="http://fonts.googleapis.com/css?family=Cantarell|Philosopher|Copse"></link>
  <link href="css/index_style.css" type="text/css" rel="stylesheet">
  <script src="https://ajax.googleapis.com/ajax/libs/jquery/1.6.2/jquery.min.js" type="text/javascript" ></script>
</head>
<body>
<header>
    <hgroup>
        <h1>Proyecto</h1>
    </hgroup>
</header>    
<section>
    <h2 class="left-only">Login</h2>
     <?php 
     echo $this->form; 
     ?>  
</section>
</section>
</body>
</html>
 

El problema es cuando le doy entrar al boton. el realiza bien todas las validaciones.
pero no esta devolviendo los mensajes de las validaciones del Zend_Form.
Soy un poco nuevo en esto y no he podido solucionar ese detalle.