CakePHP ACL tutorial initDB alert function

I follow the http://book.cakephp.org/2.0/en/tutorials-and-examples/simple-acl-controlled-application/part-two.html tutorial and I have slightly different groups (groups 4 and 5) . 4 are visitors and 5 are administrators

    function initDB() {
 10         $group = $this->User->Group;
 11         //Allow admins to everything
 12         $group->id = 5;      
 13         $this->Acl->allow($group, 'controllers');
 14        //^doesnt work
 15        //$this->Acl->allow(array( 'model' => 'Group', 'foreign_key' => 5), 'controllers');
 16        
 17        
 18         $group->id = 4;
 19         $this->Acl->deny($group, 'controllers');
 20         $this->Acl->allow($group, 'controllers/User/login');
 21         $this->Acl->allow($group, 'controllers/User/logout');
 22        /*
 23        $this->Acl->deny(array( 'model' => 'Group', 'foreign_key' => 4), 'controllers');
 24        $this->Acl->allow(array( 'model' => 'Group', 'foreign_key' => 4), 'controllers/User/login');
 25        $this->Acl->allow(array( 'model' => 'Group', 'foreign_key' => 4), 'controllers/User/logout');
 26 */      
 27         
 28         
 29         echo "all done";
 30         exit();
 31     }

but when I run this function, I get the following errors:

Warning (512): DbAcl::allow() - Invalid node [CORE/Cake/Controller/Component/AclComponent.php, line 387]
Warning (512): DbAcl::allow() - Invalid node [CORE/Cake/Controller/Component/AclComponent.php, line 387]all done

what gives?!

edit - my App Controller looks like this

<?php

class AppController extends Controller {
    public $components = array(
            'Acl',
            'Auth' => array(
                'authorize' => array(
                    'Actions' => array('actionPath' => 'controllers')
                    )   
                ),  
            'Session'
            );  
    public $helpers = array('Html', 'Form', 'Session');

    public function beforeFilter() {
        $this->Auth->actionPath = 'controllers/';
        //Configure AuthComponent
        $this->Auth->loginAction = array('controller' => 'users', 'action' => 'login');
        $this->Auth->logoutRedirect = array('controller' => 'users', 'action' => 'login');
        $this->Auth->loginRedirect = array('controller' => 'images', 'action' => 'index');
        $this->Auth->allow('display');
    }   
}


?>

EDIT 2: The full warning is as follows

Warning (512): DbAcl::allow() - Invalid node [CORE/Cake/Controller/Component/AclComponent.php, line 387]
Code Context
DbAcl::allow() - CORE/Cake/Controller/Component/AclComponent.php, line 387
AclComponent::allow() - CORE/Cake/Controller/Component/AclComponent.php, line 128
UsersController::initDB() - APP/Controller/UsersController.php, line 20
ReflectionMethod::invokeArgs() - [internal], line ??
Controller::invokeAction() - CORE/Cake/Controller/Controller.php, line 473
Dispatcher::_invoke() - CORE/Cake/Routing/Dispatcher.php, line 107
Dispatcher::dispatch() - CORE/Cake/Routing/Dispatcher.php, line 89
[main] - APP/webroot/index.php, line 96

Let me know if you want me to post any other code.