Random Posts Changes Single Thumbnail?

Recently I changed my code around. The “random posts” script I have been using for some years, I guess I for the first time put in a leftbar, loading before the single thumbnail.

The last image to load in the random posts is being loaded in full size, even though the random posts is loading a resized/cropped version.

Here is the code:

<div class='random'>
<div class='contain'>

<?php $tabs = get_option('nt_tabs'); if ($tabs) { ?><?php } else {?>
<div class="tabs">

<div class="panes"> 

<div>
<ul>
<?php
$args = array( 'numberposts' => 4, 'orderby' => 'rand' );
$rand_posts = get_posts( $args );
foreach( $rand_posts as $post ) : ?>

<li>

<a href="<?php the_permalink(); ?>" rel="bookmark" title='<?php the_title(); ?>'>
<?php the_post_thumbnail( '250-180' ); ?>
<?php the_title(); ?>
</a>

</li>

<?php endforeach; ?>
</ul>
</div>

</div><!-- panes -->
</div><!-- tabs -->

<?php } ?>

</div><!-- contain -->
</div><!-- random -->