Exact same issue with my Zune 80, albeit this from a device I've just (read: it did this out of the box) received from the Microsoft repair center! Ugh. Anyone figure this out yet? Granted, Microsoft must've bumped up their repair center a bit as when I sent in my original 80 (under warranty yet) I had a shipping box within a week, and had a replacement 80 a week later. But, like I said, it's having battery issues.
Do you think it's a bug issue with 3.1?
-w-