I also have this problem, however, it's only apparent when I have it plugged in and charging. I'm running r14031-070727
But for some reason, if I turn it off [says shutting down, then the screen turns off] and I'll turn it back on a few hours later and it'll tell me the battery is almost dead. Then it bricks for a little while and the next time I turn it on, it comes back showing nearly full battery. It's confusing [read: annoying] me.