Slide/remove leaving behind ui effects wrapper with height

Slide/remove leaving behind ui effects wrapper with height

I'm trying to implement a slide-in, slide-out deal mimicking the style at foursquare, cycling through a set of elements, only showing X at a time.  I have lifted their code pretty much directly for my first test:

  2.       <script type='text/javascript'> 
  3.         //<![CDATA[
  4.            var delay = 5000;
  5.            var count = 20;
  6.            var showing = 10;
  7.            var i = 0;
  8.            function move(i) {
  9.              return function() {
  10.                $('#feed_item'+i).remove().css('display', 'none').prependTo('#feedContainer');
  11.              }
  12.            }
  13.            function shift() {
  14.              var toShow = (i + showing) % count;
  15.              $('#feed_item'+toShow).slideDown(1000, move(i));
  16.              $('#feed_item'+i).slideUp(1000, move(i));
  17.              i = (i + 1) % count;
  18.              setTimeout('shift()', delay);
  19.            }
  20.            $(document).ready(function() {
  21.              setTimeout('shift()', delay );
  22.            });
  23.         //]]>
  24.       </script>

The problem I'm having is that as opposed to the top item sliding up and going away completely, instead it is leaving behind a ui-effects-wrapper div that has the same height as the item that was removed.  The list continues to move down the page until it cycles through and then it comes back up to the top even higher than it initially started.

Are there any gotchas on element styling or anything that could be causing this?  Or am I missing something here?