get latest post from a single category display linking thumbnail

Hi all
I have been using the code below to display the featured image of the latest post from the specified category. But it has stopped working, any ideas or better code?
Site is here the white box next to the slider is where the thumbnail used to appear.

<?php
query_posts('cat=75');
if ( has_post_thumbnail()) {
  echo '<a href="' . get_permalink() . '" >' . the_post_thumbnail() .'</a>';
}
?>

Many thanks in advance