It might. I'm on XP, I don't know about Karn. I think Vista is a bit of a joke myself, but there's no way to confirm that Vista is at fault for this problem. It may well be something else, unless we get a huge number of people in here with XP that don't have the problem and some with Vista that do.
And to answer your previous question, when I was using the gamepad I was using it for everything, yeah, including menus and such. My screensaver comes up very quickly, so if it was going to, it should have.