That may not be true: I've read of people having problems with my model of laptop when they installed the Nvidia driver instead of the version that Toshiba supply... it seems the driver on Nvidia's web site either runs the GPU faster or lets it run to a higher temperature than the Toshiba-ised version.
That was my thoughts, in a way. Laptops tend to be more temperamental as far as "generic" driver software, like Nvidia/ATi drivers, goes so I always say the first port of call is the maunfacturer's website to update/reinstall the drivers. Of course, drivers from Windows Update can have the same issues as the Nvid/Ati ones, and more issues too, so that should be avoided too (and that goes for ALL PC's, not just laptops. I've had so much trouble with things because of Microsoft's driver updates, it's beyond belief).
Overheating is a possibility/probability too, it's worth making sure all the air vents are clear and the fan "exit" has no fluff clogging it up. Also do remember that putting a laptop on your lap or on a cushion/blanket/etc "because you can" is one of the worst things you can do since that will close up air vents. Always make sure you have, at least, a newspaper under it as that will help keep the vents clear. I know it's stating the bleeding obvious but you wouldn't believe how many people think that because it says "laptop" it should be perfectly happy on a pair of jeans, etc, sucking in all the dust and fibres into it with absolutely no ill effects whatsoever..........