My Kindle (3?) would not turn on after the screen froze and I did a hard shut down. I used a combination of solutions above to fix it. I held the power button for about thirty seconds, getting the flashing green power light about 7 seconds in and then a flicker of the screen about 25 seconds in. The screen remained blank after that and I let the power button go. I then held down the Alt and R keys simultaneously and the Kindle began rebooting. It is now up and running with all of the contents that were there prior to the hiccup.