It just freezes without pixelation. Menus appear normal. The annoying bit is the spontaneous rebooting.. On rebooting it takes about 10minutes to move past the starting up prompt.
Hmm OK sounds like a faulty box that will need replacing, to do this call 0345 454 1111 at 8am sharp to avoid queues or hang around here for a few days or so and a team member should be along to help