invalid token

[mumin3k]

Hi, 
I just started writing my new module, and i have a problem with invalid token value error, here is the code:

class UltimateExporter extends Module
    {
      function __construct()
      {
        $this->name = 'ultimateexporter';
        $this->tab = 'administration';
        $this->version = '0.1.0';
        $this->author = 'me';
        parent::__construct();
        $this->displayName = $this->l('Ultimate Exporter');
        $this->description = $this->l('Under development');
      }
      public function install() {
          parent::install();
        return true;
      }

      public function getContent(){
          return $this->displayform();
      }
      private function displayForm(){
            $default_lang = (int)Configuration::get('PS_LANG_DEFAULT');

            // Init Fields form array
            $fields_form[0]['form'] = array(
                'legend' => array(
                    'title' => $this->l('Export products'),
                ),
                'input' => array(
                    array(
                        'type' => 'text',
                        'label' => $this->l('URL aplikacji'),
                        'name' => 'appURI',
                        'size' => 63,
                        'required' => true
                    ),
                    array(
                        'type' => 'text',
                        'label' => 'token',
                        'name' =>'token',
                        'size' => 511,
                        'required' => true
                    )
                ),
                'submit' => array(
                    'title' => $this->l('EXPORT'),
                    'class' => 'btn btn-default pull-right'
                )
            );

            $helper = new HelperForm();

            // Module, token and currentIndex
            $helper->module = $this;
            $helper->name_controller = $this->name;
            $helper->token = Tools::getAdminTokenLite('AdminModules');
            $helper->currentIndex = AdminController::$currentIndex.'&configure='.$this->name;

            // Language
            $helper->default_form_language = $default_lang;
            $helper->allow_employee_form_lang = $default_lang;

            // Title and toolbar
            $helper->title = $this->displayName;
            $helper->show_toolbar = true;        // false -> remove toolbar
            $helper->toolbar_scroll = true;      // yes - > Toolbar is always visible on the top of the screen.
            $helper->submit_action = 'submit'.$this->name;
            $helper->toolbar_btn = array(
                'save' =>
                array(
                    'desc' => $this->l('Saves'),
                    'href' => AdminController::$currentIndex.'&configure='.$this->name.'&save'.$this->name.'&tab_module=administration&module_name=ultimateexporter'.
                    '&token='.Tools::getAdminTokenLite('AdminModules'),
                ),
                'back' => array(
                    'href' => AdminController::$currentIndex.'&token='.Tools::getAdminTokenLite('AdminModules'),
                    'desc' => $this->l('Back to list')
                )
            );


            return $helper->generateForm($fields_form);
        }
    }

and every time when i click 'save' button I get 'invalid token' error but when I copied action property value from generated form and pasted into adress bar in browser everything works fine. Do you have any ideas what is wrong?