In both IE6 and IE7, when the draggable is an image, it is not easily
accepted in the droppable area.
When a user that is not very quick in dragging and dropping an image
into the container, his cursor will change to the 'not-allowed' state,
and he will not be able to drop the image (without beginning to drag
it again)
Here is some test code to try out this bug yourself:
http://pastie.org/244429
Many thanks
(the test uses google's hosted prototype1.6 and scriptaculous1.8.1, so
you can use the test right out of the box)