you just forgot to close the ul :o)
<?php
//exclude the "_*" custom fields and "enclosure" when displaying in loop
if ( $keys = get_post_custom_keys() ) {
echo "<ul class='post-meta'>\n";
foreach ( (array) $keys as $key ) {
$keyt = trim($key);
if ( '_' == $keyt{0} || 'enclosure' == $keyt )
continue;
$values = array_map('trim', get_post_custom_values($key));
$value = implode($values,', ');
echo apply_filters('the_meta_key', "
<li><span class='post-meta-key'>$key:</span> $value</li>
\n", $key, $value);
}
echo "</ul>\n";
}
?>
