I've had this same problem since the very first Fences beta and it's still happening in the latest version (I've posted about it before, but got no reponses):
About half the time, I lose ALL Desktop drag-n-drop functionality where I can't drag icons around my desktop at all - I get the black-circle-with-slash-thru-it when attempting to drag.
Anybody else experiencing this issue? Any help will be much appreciated.
JohnB