I have a Sony Vaio and it's been working perfectly for about a 18 months.
All of a sudden the video is failing. Either on boot or after or once Windows Vista is up and running it suddenly goes black screen although the computer continues to run normally.
Although I say black screen if I tilt the screen right back and look at it at a very shallow angle in a strong light I can just about make out what is on the screen and everything else continues normal.
If I force the computer to hibernate and then reactivate it, it comes back normally and then runs OK for the rest of the session no matter how long I use the computer.
Last night I updated the driver to the latest available on the Sony support site 188.8.131.525 but it made no difference.
Tonight the computer booted up to a black screen, I again forced it into hibernation, then touched the On button, it came back perfectly and the screen was then normal.
I'm beginning to think that my chipset is gradually failing.