Error in droppable.js

Error in droppable.js


Hi guys ,
I am using the droppables.js on my site and this js file was directly
linked to teh jquery.
Today I found a bug in teh droppable.js file.For some resons its
giving a helperSize.width javascript error on the browser and also has
forced teh functionality to not work.
You can also this error on teh following page
http://docs.jquery.com/UI/Droppables
Just try to drag and drop the element.
Any idea on why this has come up and what needs to be done to resolve
this.