Thumbnails missing after add_filter

Hi All,

I added the following call to my functions.php and have now lost the thumbnails on my home page.

Any suggestions? If I comment out the call to add_filter then they show up again.

# Pre-fetch for posts
function setcat_pre_posts($query) {
	if ($query->is_home) // Assuming you want this to apply when it's your home page
	{
	  $domain = preg_replace("/^(.*\.)?([^.]*\..*)$/", "$2", $_SERVER['HTTP_HOST']);
	  $domainstr = substr($domain, 0, -4); 

          $sitecat_id = get_category_by_slug($domainstr)->term_id;
          $generalcat_id = get_category_by_slug('general')->term_id;
          $cats = $sitecat_id.','.$generalcat_id;
          $query->set('cat', $cats);
	}
	return $query;
}

add_filter('pre_get_posts', 'setcat_pre_posts');

I should probably post this as well. Here’s the code being used in functions.php to get the thumbnail.

# Displays post image attachment (sizes: thumbnail, medium, full)
function dp_attachment_image($postid=0, $size='thumbnail', $attributes='') {
	if ($postid<1) $postid = get_the_ID();
	if ($images = get_children(array(
		'post_parent' => $postid,
		'post_type' => 'attachment',
		'numberposts' => 1,
		'post_mime_type' => 'image',)))
		foreach($images as $image) {
			$attachment=wp_get_attachment_image_src($image->ID, $size);
			?><img src="<?php echo $attachment[0]; ?>" <?php echo $attributes; ?> /><?php
		}
}