Custom field issue

I am querying posts on a page template and i am having a problem with custom fields not displaying after the loop. They display fine before the loop though. Any ideas?

Thanks

<?php query_posts('posts_per_page=4'); ?>
		<?php while ( have_posts() ) : the_post(); ?>
               <?php endwhile; ?>

<?php echo get_post_meta($post->ID, "post description", true); ?>