I see this on all our windows 7 workstations once in a while, and i think like Todd it is some graphics card/driver related. It seems like it fights over screendrawing, and i have only seen it with AE, but im not blaming AE to be the problem, it just happens i spend ~90% of my time in AE so it usually is seen with AE :-D
I can fix it by quickly pressing the Windows key to bring up the start menu, that seems to force a redraw of the screen and everything is back to normal.
Now that you are on Win8 the win key of course works a bit differently. Maybe try to press Win+C to bring up the clock and Charms menu and see if that forces a redraw too and stops the flickering.
Robert