Same thing happened to me yesterday, 1 hour before England kicked off
The box froze, I unplugged it then restarted it and the lights flash on and then off. Holding standby down for 5 or so seconds displays SToP but nothing else happens. I can hear the hard disk whirring and clicking, even though the lights are not on.
I thought perhaps by switching off at the back and unplugging while the box was frozen may have corrupted or broke the hard disk?
Luckily I still had the old box (non-HD) so I could use that to watch the game. No engineer until Wednesday though.