[jQuery] submenu doesn't hide

url: bldd.nl/jsproblems/convertToJQuery.html

this part of my code doesn't seem to work

------------
alert($expandedSiblings.size());
if ($expandedSiblings.size() > 0) {
$expandedSiblings.slideUp(500, function(){
$heading.find('ul').slideDown(500);
});
}
----------------

an already opened submenu isn't closed???

regards