I thought the same thing. So i started in safe mode and removed the 305.XX (for the 660 this is most current) driver. when i did this, i was able to get past the blue screen but obviously, i had no graphics driver. Thinking it may be the driver, rolled back to legacy drivers 296 and 285 nvidia drivers and all have the same problem.
Could CPU heat do this? and also, a much more annoying theory is, has the motherboard simply given up on life?