I have had this happen to my to both my laptops within a week, first my Windows HP Laptop developed this problem which is far more worse btw and now my macbook pro 13 (2011 model). For my Windows laptop I figured it could be over heating that messed up the video card (there is also a noise coming from it also). I do not have enough proof thoug that it over heated. Usually if it lays on bed for longer period, it definitely overheats but we are careful about it. About my mac, it was totally cold. I use it last night (downloaded a torrent) and I shut it down completely. I know it was not overheated because it was in my lap. This morning I turned it on and I see this problem. Notice the edges around the window and colors are messed up to in places.
Anyone can think of what could be problem. I am outside US so can't really take it to Apple store. Thanks