[X4U] Cancelling Mouse Action

[Jon Warms]

 From the very first Mac OS, it had been possible to cancel a mouse  
action by dropping the object in the menu bar. This no longer works,  
the object is dropped on the window under the menu bar (often the  
desktop). In other words, you used to be able to change your mind on a  
click-drag operation by dragging and dropping the object on the menu  
bar.

In Leopard (10.5), is it possible to cancel a mouse action "in flight"?