Seeing the same issue with a GeForce Go 6150 in an HP Pavilion tx2000.
It's worth noting that the problem isn't specific to Unity. Pretty much anything 3D runs dog slow if it doesn't freeze or crash outright. glxgears on my system gives a depressing 5fps.
Like others, reverting to 295.33 fixed the problem.
When I have time, I'm going to try applying the security fix to the 295.33 module and see if the problem comes back.