This happened to me two weeks ago. I was playing Dead Rising and the same exact thing happened. I restarted several times only to get frozen either at boot up or some point in navigating the dashboard.
I got it working a few days later (it'll probably happened again lol i hope not).
Here's what I did.
Unplug everything including the hard drive.
Let it sit for a day.
Connect everything back.
Boot and do the hard drive maintenance (X, X, Left shoulder, X, X, Right shoulder)
Restart your console.
If it's not working then it could be corrupted data on your hard drive from the game that frozed. Sadly, you might just have to delete your LO save. Or maybe back it up and transfer it back. If that doesn't work, then you might have to reformat your entire hard drive.
And if that doesn't work, well fuck you microsoft!