So this has been going on for probably 6 months at least but I've never bothered to ask about it. Whatever window I'm in will randomly minimize. It doesn't seem to matter if I'm gaming or just browsing the web. Just once every hour or so, it will just minimize whatever my active window is. The one exception is if I'm watching something in netflix full screen, instead of minimizing it will just drop me out of fullscreen mode (annoying if I'm cooking or something and don't notice and my computer locks because netflix isn't fullscreened anymore.)
I have a friend having the exact same problem as well.
We're both running Win 7x64, but that's about the only real commonality as far as setup.