This has been discussed before, but usually as a once in a while event.
It does happen to me about once a month at most.
I know it's going to occur when I don't see the blue LED flash when I hold down the power off button. Then it goes to the sleep mode. I then have to push the button again to get back to the book, and sometimes it will reboot at that point. Then I'm able to power it off.
ltr
|