robinburrer on "Nested custom post type pagination"

Hi forum,
after spending almost a day on this problem I hope that you can help me.
I have a custom post type "employee". In a wp_query I want to display all entries and want to have them paginated as well. That all works - on a regular page it does at least.

However if I insert the same code on my "single-institution.php" (institution is a custom post type as well that ) the pagination does not work anymore. It shows up, it links to the "correct" page (page/2/) but the link always leads back to the first page. It seems the following pages are not generated at all.

So is this possible at all? Can I have a working pagination for a custom post type on a "single-custom post type page"?

This is what the query code looks like:

$args=array(
           'post_type' => "employee",
           'post_status' => 'publish',
            'caller_get_posts' => 1,
            'orderby'           => 'menu_order',
           'order' => 'ASC',
           'posts_per_page' => 3,
           'paged' => $paged
            );

$temp = $wp_query;
$wp_query = null; 

$wp_query = new WP_Query($args);

// then I loop through the query

previous_posts_link('« Newer') ;
next_posts_link('Older »');

 wp_pagenavi(); 

//wp_reset_query();  // Restore global post data stomped by the_post().    

// Reset the  query
$wp_query = null;
$wp_query = $temp;

The argument array of the "institution" post type lools like this - in case this could be relevant:

$args = array(
         'label' => __('Institution'),
         'labels' => $labels,
         'public' => true,
         'publicly_queryable' => true,
         'show_ui' => true,
         '_builtin' => false,
         'show_in_menu' => true,
         'query_var' => true,
         'rewrite' => array("slug" => "in"),
         'capability_type' => 'post',
         'has_archive' => true,
         'hierarchical' => true,
         'menu_position' => 20,
         'supports' => $supports
      );

All help is appreciated!

Robin