Damn, some thing moved in my kitchen again.  Last week while I was putting groceries away, I sat a box of Stove Top Dressing in the floor.  I have a concrete floor.  I was across the room putting stuff away, and I saw the box fall over.  The furnace was not on, so there was no air movement.  The box was perfectly square.  So far the box hasn't moved since.  I really do think there's a logical reason.  But it happens so often that I just can't explain it.  Weird...