Why is MBP 15" screen flickering and freezing?

My MBP (15") is freezing and flickering. Not sure why.

It is also timing out and I get the circle rainbow for at least 30mins. Then after that, if I can move the mouse pointer, parts of the screen turn into boxes and start breaking up into the background. I tried to lower the resolution and seemed to work for a few hours, but if I make a quick movement of click too many application boxes it freezes and the mouse pointer erases the open windows.

What is this about?

Do I have to repair the video card or something?