My son updated his XBO tonight and had an interesting problem. First he updated the console then he updated his Plants vs Zombies Garden Warfare and that is when he noticed there was no sound. We tried to go to settings but the settings screen would open then boot us out. So we power cycled and still had a problem. We followed that wish a reset (power button & eject button) and the problem still persisted. At that point I also found out I couldn't open any of his apps either. That lead me to try unplugging the console and then plugging it back in. Then on start-up sound was back and we could access his settings and games.
Just thought I would share this with everyone. I have not had this problem on my console but I am getting the beta updates so I am not sure if this is a regular thing happening or not.