[Resizable & Draggable] Element jumps up & left after resize in Mozilla

The code below produces a draggable and resizable div, as expected. However, once this div is resized for the 1st time, subsequent resizes and drags cause the div to jump a bit to up & left. This happens only in Firefox (3.0b5pre). Opera and IE work fine.

<script src="jquery/jquery-1.2.3.js"></script>
<script src="jquery/jquery.dimensions.js"></script>
<script src="jquery/ui.mouse.js"></script>
<script src="jquery/ui.draggable.js"></script>
<script src="jquery/ui.resizable.js"></script>
<script>
  $(document).ready(function() {
    $("<div id='aaa'></div>").resizable()
                             .draggable()
                             .appendTo(document.body);
  });
</script>
<style>
  #aaa {
    width: 100px;
    height: 100px;
    background-color: lightblue;
    border: 1px solid black;
  }
</style>