add: Sortable.options(oldParentNode).onChange(element); Sortable.options(dropon).onChange(element); 
context:   onEmptyHover: function(element, dropon) {    if(element.parentNode!=dropon) {      dropon.appendChild(element);    }  },
meta: 7994	/local1/tlutelli/issta_data/temp/all_js/javascript/2006_temp/2006/7994/969f72945d4b0fbac31e07c8140508d42e5c4c0f/dragdrop.js/buggy/src/dragdrop.js