add: Sortable.options(oldParentNode).onChange(element); Sortable.options(dropon).onChange(element); 
context:   onEmptyHover: function(element, dropon) {    if(element.parentNode!=dropon) {      dropon.appendChild(element);    }  },
meta: 1331	/local1/tlutelli/issta_data/temp/all_js/javascript/2006_temp/2006/1331/8a342036a177e27b9f776c900bbae999b6ce8e3c/dragdrop.js/buggy/tracks/public/javascripts/dragdrop.js