I have found it!
On both files (controllers/front/NewProductsController.php) and (controllers/front/CategoryController.php) change the code from
public function setMedia()
{
parent::setMedia();
$this->addCSS(_THEME_CSS_DIR_.'product_list.css');
}
to
public function setMedia()
{
parent::setMedia();
$this->addCSS(_THEME_CSS_DIR_.'product_list.css');
$this->addJqueryPlugin(array('fancybox', 'idTabs', 'scrollTo', 'serialScroll', 'bxslider'));
}
To make it work on Startpage you have to edit the file controllers/front/IndexController.php too.
Change
parent::initContent();
$this->addJS(_THEME_JS_DIR_.'index.js');
to
parent::initContent();
$this->addJS(_THEME_JS_DIR_.'index.js');
$this->addJqueryPlugin(array('fancybox', 'idTabs', 'scrollTo', 'serialScroll', 'bxslider'));
That will do the job!