Hi garner
A couple of posters have said there box has updated to version 5.14 so it's possible that yours has tried to perform this update and failed.
Have you tried removing the actual box from the mains for 5 minutes?
If that doesn't work there are three possible workarounds.
Try turning off the 360 by the switch on the back of the box; then on the front of the 360 box hold down both the power button and the - (minus) button at the same time. Then turn on the 360 again whilst keeping hold of those buttons for a further 30 seconds.
If the power button and the - button workaround doesn't solve it then try using the power button and the + (plus) button at the same time instead.
You could also try the three fingered salute, which is switch off on the back of the box; then on the front hold down the plus, minus and power buttons at the same time, and switch on again whilst keeping all three buttons pressed down. When it restarts you might see a message it can't acquire the channels. If so press OK and let it restart again.