Scrollbars from layers below show Draggable if zIndex is set Firefox Mac

If you drag a Draggable window over a layer with scrollbars on Firefox 2 for Mac the scrollbars of the layer underneath will push through.

Example: http://metronomy.kipparker.co.uk/scrollbars.html (the window headings are the handles)

I wonder if this was the same problem?

http://dev.jquery.com/ticket/2450