I was having that problem too but my video card is not nearly as nice as the one one you have. I figured it was a driver or something. I did my best to update the driver, but could not find the right download to fix it.
A friend told me to try Driver Boost www.driverboost.com and it fixed the problem. It cost about $30.00 usd, but it was worth every penny. It also updated several other drivers.