FWIW, mine is also going wonky. Funnily enough, in my long trail of devices, that's the only battery/device I've ever seen go truly bad. (I'm pretty sure my old K2i is still kicking, for instance).
It's... kinda weird. The last time I actually used it was actually to test power consumption, and the numbers looked good; but I've since seen it drain while in suspend, while *off*; and I've seen it hang in fun and interesting ways while *charging*

.
EDIT: To be perfectly fair, it's also the only device I've somewhat extensively used in extremely out of specs conditions (namely, well below 0°C). The battery didn't take it well, even back then ^^.