IE: drag thumb on scrollbar in sortable item tries to drag sortable item

Hi Ed,

thank you for your feedback - I noticed that you commented in the issue, too. Unfortunately, the addition of IE 9 does not help much in the resolving of the issue - we haven't figured out how to detect clicks on the scroller, apart from the very crude and error-prone pixel measuring. If we do this, it may affect our performance seriously. 

Regards,
Petyo
Telerik