Run a video card stress test, 3dmark should do the trick. See if the display corruptions shows up. When they scramble, do they go back to normal on it's own or do you need to shut the laptop down?
oops, it looks as if I was supposed to reply directly. however, my reply is below in another post. The summary is that I think that getting the screen to refresh makes the problem go away. I'll be doing some further work, I guess.