It's probably the UAC monster. A program without admin priveleges may not be able to disable the power saving features.
You could right-click, Run as Administrator on MC to test.
We'll look on our end as well.
I've had really bad luck with Vista's power savings. It bombs on S3 standby for me, even though XP worked great on the same hardware. I fought with it a lot, and then finally gave up.