As an anecdotal (counter?)datapoint, I've been running Win 7 64 bit since it was released; at least a couple years now, and have never seen this behavior.
I'm using the "nt emacs" from sourceforge (http://ntemacs.sourceforge.net/). I can't say definitively that I have, or have not, ever had a week or more of uptime with the box as a whole, or with emacs, but it doesn't seem outside the realm of possibility. Never had any weird windows or frame moving experiences with it that I can recall.
