Begindrag: you drag the object above all objects because of z-index:1000
Enddrag: you see the element dissappear behind the elements which are later in DOM tree on its way to starting position.
Solution. Retain the zindex: 1000 until the revert is finished.
==My own hack:==
*finishDrag function:
**moved zindex to org zindex revert parameter set to before revert function.
*reverteffect function:
** added: element.style.zIndex = this.zindex;
** added following options to move Effect:
*** afterFinish : function(obj){obj.element.zindex = this.originalZ;},originalZ : this.originalZ