I'm out of ideas at the moment. It's all rather unfortunate as the whole system dies and there is no way to save a log or anything. It would be possible to log it through serial through ext connector, but that needs a special cable or debug board that nobody is making, not even ED himself. If you can find anything that causes the problem to appear/go away let us know.. There is an option in LCD settings but I haven't tested that personally (it was added by ED). Edit: what ebook reader are you using, BTW?