Get Post – strange behaviour

Hi, I use the code below to display a random page from a certain post parent. The excerpt seems to work the first time the page is loaded then does not refresh / update again!.

Can anyone spot the problem? Thanks for your help.

<div class="box">
	<div class="service-box">
		<h3>Services</h3>
		<?php  $rand_posts = get_posts('posts_per_page=1&post_type=page&post_parent=35&orderby=rand'); foreach( $rand_posts as $post ) : ?>
    	  <div class="box-inner">
		  <span><?php the_title(); ?></span>
		  <?php the_excerpt(); ?>
		  </div>
		<a href="<?php the_permalink(); ?>" class="button">Find out more</a>
       <?php endforeach; ?>
	</div>
	<?php wp_reset_query(); ?>
</div><!-- end box -->