Navigtion issue (sub sub)

Hello,

I am trying to make seperate navigations. The basic outlay:
main menu
sub menu

sidebar: sub sub

I have the following code for this:
sub menu:

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

sub sub in sidebar:

/* Fetch the pages, if there is a <ul> in the list it means that we haven't reached lvl 3 so don't do anything :) */
		if($post->post_parent != 0)
		{
			$subsub = wp_list_pages('echo=0&title_li=&child_of='.$post->ID.'&depth=2');
				<ul id="subsub">
				<?
				echo $subsub;
				?>
				</ul>
		}
		?>

The problem is, once I visit a sub sub page, the sub sub menu is listed in the sub menu, the sub menu is gone (main menu is listed manualy), and the sub sub menu is empty.

I though I could do a workaround by checking with post_parent how deep I am, but it doesn’t seem to work like this:
`$a = $post->ID;
$b = $a->post_parent;
$c = $b->post_parent;´

any help here would be much appreciated ^^