Issue with rendering a template from a plugin function
I haven't tried calling a template from a controller, so I may not be any help but I've used

...-&gt;render(...)


in my main plugin Class like this:

MyPlugin.php

return craft()-&gt;templates-&gt;render('myplugin/_settings', array('settings' =&gt; $this-&gt;getSettings()));


Maybe the render method is looking for another argument?

EDIT

Oh wait... I was wrong, it looks like I do...

MyPluginController.php

$vars['users'] = craft()-&gt;user-&gt;listUsers();
$this-&gt;renderTemplate('myplugin/index', $vars);


Then I have a variables file:

MyPluginVariable.php

public function getContacts()
{
    return craft()-&gt;contactForm-&gt;getUsers();
}


Which ties back to the my service:

MyPluginService.php

public function getUsers()
{
    return MyPluginRecord::model()-&gt;findAll(array('order' =&gt; 'dateCreated desc'));
}


Maybe that will help get you rolling?