Vorlage für Gallerie - Navigation funktioniert nicht

<?php
/*
Template Name: gallery
*/
?>


<?php get_header(); ?>
        
        <div id="home_content" class="column span-14">   <!-- start home_content -->


<div id="home_left" class="column span-11 first">


<h2 class="archive_name"><?php the_title(); ?></h2> 
        




<?php $the_query = new WP_Query('category_name=bilder');
            
                    while ($the_query->have_posts()) : $the_query->the_post();


                    $do_not_duplicate = $post->ID; ?>
 <div class="galoverview">
         
        <?php $attachments = get_children(array('post_parent' => get_the_ID(), 'post_type' => 'attachment', 'post_mime_type' => 'image', 'orderby' => 'menu_order'));
        if ( ! is_array($attachments) ) continue;
        $count = count($attachments);
        $first_attachment = array_shift($attachments); ?>
       <div class="set">
        <a href="<?php the_permalink() ?>">
                <?php echo wp_get_attachment_image($first_attachment->ID); ?> 
        </a>
        </div>
        <div class="galdescription">
        <h3 class="archive_title"><a href="<?php the_permalink() ?>"><?php the_title(); ?></a></h3>


<div class="archive_post_meta">Von <?php the_author_posts_link(); ?> <span class="dot">&sdot;</span> <?php the_time('F j, Y'); ?> <span class="dot">&sdot;</span> <a href="<?php comments_link(); ?>"><?php comments_number('Kommentieren','Ein Kommentar','% Kommentare'); ?></a></div>


                <?php the_excerpt() ?>
        <p>Diese Gallerie enth&#228lt <?php echo $count ?> Bilder.</p>
        </div>
</div>
<?php endwhile; ?>


            <div class="navigation">
                    <p><?php next_posts_link('&laquo; Vorherige Galerien') ?> — <?php previous_posts_link('Naechste Galerien &raquo;') ?></p>
                </div>                    
                
            </div>
               
            
            <?php get_sidebar(); ?>     
            
        
        </div>   <!-- end home_content -->
        
        
<?php get_footer(); ?>