I didn't have that bug in win7 . On my new pc with win8 I constantly get a kind of frozen square area/patch on the screen.
It's indistinguishable and looks like everything just stopped responding till you shift or rotate the scene. After that it appears like a piece of max viewport screenshot above anything else. It stays on screen even if you minimize Max , until you completely close the program.
Do anybody know how to fix it or what may cause that bug?