Function problem with Brian’s Latest Comments

I get this message underneath my Latest Comments:

Warning: Invalid argument supplied for foreach() in Line 87

And in the PHP file (incl Line 87):

foreach($posts as $post)
{
// The following 5 lines is a manual DISTINCT and LIMIT,
// since mysql 3.x doesn’t allow you to control which way a DISTINCT
// select merges multiple entries.
if(array_key_exists($post->comment_post_ID, $seen))
continue;
$seen[$post->comment_post_ID] = true;
if($num++ > $num_posts)
break;

Any idea where I am going wrong?