<h2>Related Posts</h2>

<!-- "previous page" action -->
<a class="prev browse left"></a>

<?php

 $tags = wp_get_post_tags($post->ID);
 if ($tags) {
     $tag_ids = array();
     foreach($tags as $individual_tag) $tag_ids[] = $individual_tag->term_id;

 $args=array(
'tag__in' => $tag_ids,
'post__not_in' => array($post->ID),
'showposts'=>12, // get all the posts at once, then split them up afterwards.
'ignore_sticky_posts' => 1
 );

$posts_per_block = 4;

$my_query = new wp_query($args); ?>

<!-- root element for scrollable -->
<div class="scrollable" id=chained>

    <!-- root element for the items -->
    <div class="items">

<?php
if( $my_query->have_posts() ) : while ($my_query->have_posts()) : $my_query->the_post();
if ( ($my_query->current_post) == 0 ) {
    echo '<div>';
}
elseif ( ( $my_query->current_post ) % $posts_per_block == 0 ) {
    echo '</div><div>'; //close and open a new div every nth post
}
?>

<div class="relatedPosts"><a href="<?php the_permalink() ?>" rel="bookmark"><?php the_post_thumbnail(array(120,80)); ?></a>
<div class="relatedPosts_title"><a href="<?php the_permalink() ?>" rel="bookmark" title="Permanent Link to <?php the_title_attribute(); ?>"><?php the_title(); ?></a></div></div>

<?php

if ( ( $my_query->current_post + 1) == ( $my_query->post_count ) ) {
    echo '</div>'; //close the block if you run out of posts
} ?>

<?php
endwhile; endif;
?>

    </div>

<?php } // end if($tags) ?>

</div>

<!-- "next page" action -->
<a class="next browse right"></a>