>What in the world could/would cause memory to move between the time you get
>the pointer and when you do a block move?

Nothing.

Contrary to popular belief, BLOCKMOVE does *not* affect handles. It moves 
memory from one place to another and that's it. You do NOT have to lock a 
handle if all you're going to do is blockmove in or out of it. It simply 
cannot cause your handles to move.

>Is memory something that can move at any time without cause? Or is it
>something that can move when we do something to memory that alerts the
>memory manager?

Memory cannot move "at any time without cause." It can ONLY move when you 
call the Memory Manager, or anything that calls the Memory Manager 
(Resource, Window, Dialog, File, Event, and GWorld managers are a few of 
the unsafe ones). In other words, most of the Toolbox.

Memory can only move if you give it a chance to. 

-Mars