Graphics(1680, 1050, 32)
I think this will make graphics window which is covered by the upper part of the Vista Start button. That will cause random behaviour in 3D apps, some may be depending on idle timers, and it might mess them up.
Try to make a smaller window, or use fullscreen, so that the Vista Start button does not overlap on your graphics window.
You could also use Windows 2000 theme to get some additional FPS in 3D games, and to avoid this Vista bug too.
They "fixed" this Vista bug in Win 7 by making the start button not come over the task bar.