Hey telerik...
I've a cross this "error" when testing my new drag and drop feature on my site.
I tried both local and on your demo site, same result.
It's looking like the ListBox is leaking a bit, when I go "crazy" with the drag and drop.
The selected items get stuck on the cursor, and the whole site hangs.

Is there something i can do to fixs this?

See videos of the problem here:
http://www.screencast.com/t/JzcXehBvd9BJ
http://www.screencast.com/t/7lcJz91cvMhr

Hi,

Indeed there is an issue with quick drag and drop between two RadListBox controls for example. We are aware of this problem and it is logged in our system. Here you may find the public item for this bug so you can vote for it to increase its priority and track its progress.

Regards,
Boyan Dimitrov
Telerik