Why is my image doing this (pic)?

this happens mostly during watching videos or playing games. when i turn my monitor off then on again, the problem goes away. my monitor is quite new. a viewsonic 27" vx2753mh-led bought about 6 months ago. the reason i bought this one is because my old monitor (which was old) started doing this every 20 minutes idle or not. my video card is a Radeon HD 6850 which is cooled well, updated drivers and direct x. sometimes, when playing games, the screen just flickers and shows a blank lighted screen and the computer unresponsive. after a hard restart, it shows that a blue screen had happened.