Video issues - NVIDIA GeForce GT 330M

I have problems with image on internal display on my MBP 15' (Mid 2010). It has NVIDIA GeForce GT 330M and Intel HD. The part of the image (a square about 20% of the screen) freezes and blinking while the resto of the screen changed many times. It continues up to 2 minutes. Also sometimes the image sontracts and moves to the left half of the screen, it's flicks and almost b&w. A while ago I heard about similar problems with MBPs by those had GeForce 8600M GT. http://support.apple.com/kb/TS2377

Does anyone know what can it be?