I know this question is almost two years old, but what the !&&*... I had the same issue, doing a hard reset (factory reset) resolved the issue for me, and the device had no issues booting afterward. Hold down the volume up button and press the power on button. When the splash screen with the dog pops up release both buttons. In a few seconds you'll get an android menu with several options. Choose erase all user data/factory reset and let the device cycle through the reset. It will take a few minutes, but eventually it will boot all the way.