This time I didn't lose it, or drop it and break the screen, or crush it in a door and break the screen, or anything. It just broke. Apropos of nothing, it stopped responding for a few seconds -- which has happened before -- but turning it off and back on only helped for one command, and even that only worked twice. I got it back to the main screen where a little spinny progress meter was spinning for a while... and then stopped spinning.
Now it won't respond at all, not even to the 'hard reset' command. And windows doesn't even recognize it as a device ('unkown USB device'). I think it's broken.