I understand that Drag and Drop does not support folders. However it looks like the error handling needs to be improved.
1) Under Resources choose Upload File, on any folder or root
2) Drag a folder to "Drop Files Here to Upload"
3) Use Refresh button to get back to Resources home
4) An item with no name shows up with size of $item.size
5) Click on item and then Remove button. "Are you sure you want to delete?". Size shows $member.size
6) Sakai presents message "The resource null is locked and cannot be deleted." , and it does not delete the item.