title: jquery-ui sortable wrong position of the dragged item after using a shadowbox
body: <p>I've a strange behavior when using jquery-ui sortable.</p>
  
  <p>I am using it for sorting some formsets. It works ok. However if I open and close a <a href="http://www.shadowbox-js.com" rel="nofollow">ShadowBox</a> popup, then the sortable doesn't work properly anymore.</p>
  
  <p>I don't see anymore the dragged item because of a wrong position. I've logged the dragged item position in the <code>over</code> event and see that the top position is not correct. It seems to me that the original event offset is missing.</p>
  
  <p>Any idea, how to fix this issue?</p>