I don't have a recipe starting from "emacs -Q", but with my normal
setup, opening a new frame (and then resizing it, perhaps?) makes the
area the frame takes up not repaint at all (or something like that).  So
dragging a different window over the area leaves trails.

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no