Reply times here can be as much as a week, so I hope you don't mind waiting, or paying for a service you cant use. The best time to phone is around 8am when the lines are least busy & you have a good chance of getting UK call staff.
As far as the box is concerned, PSU failure is the most likely cause, so it will be swapped.
Cable customer since 1993. Services: FH TV, Sky Sports & Movies (2xV+), Talk Unlim Telco, VIVID 100, Virgin PAYG Mobile
Firstly I'd like to welcome you to the forums and say that I'm really sorry to hear that you've been having this issue with your V+HD box, and I'd really like to help you out.
I've attempted to locate your account using your forum credentials, however have been unable to do so. I'll send you a private message in order to ask some further questions which will enable me to locate your account and run the necessary testing.
Please look to the top left of this page where you'll find a red envelope icon. Click on this and you'll see my message.