I was having this issue 24 hours after my console worked perfectly. Anytime i turned the xbox on it froze after green screen or upon kinect signing my profile in. I was able to get signed in by disconnecting my kinect and starting a game. this forced the console to sign me in and would let me move around the home screen. Once i got this far i noticed that tv and other apps were not functioning correctly. I plugged the Kinect back in at this point to find that while i could play games i was unable to do voice commands with the Kinect.
Another issue that arose is nothing that required the keyboard to populate worked. aka messages, sign ins for apps, and even changing system setting where it would require a drop down menu did not work.
well here is how i fixed this issue:
1) press and hold the power button on the console for 15 seconds.
2) unplug power supply from wall and console
3) unplug router or turn off wifi
4) wait 30 seconds then replug in your xbox power supply and turn the system back on
5) your console should boot fully and auto sign you in via Kinect
6) if you don't freeze and have all your functions back then feel free to restart your wifi and your problem should be solved!