Is about a Driver Issue but if this is a system that has been working for a while now I've seen messages like this which have been relating to Heat Issues.
Does the system shut down and restart or just turn off?
If it restarts open the case and clean out all of the dust bunnies. {Pay p[articular attention to the CPU Heat Sink which needs to be cleaned.
If this is a NB you can use Canned Air to blow out the Airways and I would suggest a Cool Pad under it at all times like the one here from Antec
http://www.antec.com/Believe_it/product.php?id=NzI=
There are other Cool Pads available and you can probably get cheaper ones on E Bay or the like. ;)
Col