When your template is using the zen17 framework, it might load the articlehelper class without checking if the class is already loaded. Even when the module is disabled in the module manager, this can cause a fatal error when used with Frontend-User-Access and Access-Manager.

Here is how to fix that:

file:
modules/mod_zentools/includes/zenj17contenthelper.php
line: 19

require_once JPATH_SITE . '/components/com_content/models/articles.php';

replace with:

if(!in_array('ContentModelArticles', get_declared_classes())){
 require_once JPATH_SITE.'/components/com_content/models/articles.php';
}