Subpages on search results

I add subpages to my theme, and they are normally displayed except on search page. The page lists all subpages when showing search results for not found.
I have this code in my header.php:


<div >
<ul id="mainmenu">

<?php wp_list_pages('depth=1&title_li='); ?>

<?php
if($post->post_parent)
$children = wp_list_pages("title_li=&child_of=".$post->post_parent."&echo=0");
else
$children = wp_list_pages("title_li=&child_of=".$post->ID."&echo=0");
if ($children) { ?>
<ul id="submenu">
<?php echo $children; ?>

<?php } ?>

<!-- SUBMENU -->

</div><!--[if !IE]>end #main-menu<![endif]-->

Thanx.