I am running Windows 7 64-bit (with all visual effects disabled). When I play fullscreen games and switch to another window via Alt+Tab, and later try to switch back to the game again by the same method or by clicking on it in the task bar, it sometimes doesn't work.
Usually, the result is that the window will appear selected in the task bar, and I can hear audio from the game, but there is no video.
However, other times I don't have this problem. For example, with Fallout 3, simply switching back to its window usually restores the game with no issue.
With Skyrim, I've noticed something very odd. If I switch back to the window, it's the audio-but-no-video issue. But, from this state, if I press Alt+Tab once and then click the left mouse button once (on a "blank" area, like the desktop background, but not something like a button in another window) the game is restored. I have no idea why this works.
However, this little trick does not work on Fallout on the occasions when it gets stuck.
I am hoping that there is a sure-fire way to force Windows to redraw the game window.