You need to turn off with the rocker switch at the back of the box, then hold the + and standby buttons together and then turn the box on and wait till you see the welcome screen. If that fails you need to call in and report a fault.
You could try the text messaging service.
Just send a text with a description of TV Faults to 07533 051809. Your message will go into a queue and a representative will respond to you as soon as possible. It may take a few days.
You can also call 150 from your Virgin landline, or 0345 454 1111, options 1,1 and 2 faults, butbest to call at 8am to avoid call queues.
The Service you do for others is the rent you pay for your room here on Earth - Muhammad Ali