Submenu problem WordPress 2.7

I updated to WordPress 2.7 I have a problem with the code below:

<?php if($post->post_parent) { $parent = get_post($post->post_parent);
	if ($parent->post_parent) {
		$children = wp_list_pages("depth=1&amp;sort_column=menu_order&amp;title_li=&amp;child_of=".$parent->post_parent."&amp;echo=0");}
	else {
		$children = wp_list_pages("depth=1&amp;sort_column=menu_order&amp;title_li=&amp;child_of=".$post->post_parent."&amp;echo=0"); } }
	else
		$children = wp_list_pages("depth=1&amp;sort_column=menu_order&amp;title_li=&amp;child_of=".$post->ID."&amp;echo=0"); if ($children) { ?>
	<ul>
		<?php echo $children; ?>
	</ul>
<?php } ?>

It should only show the submenu of the current page your on. But for some reason this is not working anymore in the 2.7 version. I did look around the forum but couldn’t find anything useful, I hope someone can help me out because I a pretty stuck at this point.