Possibly a faulty hard drive, can you pause and rewind live TV, if you can't and don't have any recordings you could try a factory reset of the 360, and as you haven't got any recordings you might as well go for the format disk option.
If the problem is still the same after a factory reset then you need to call Virgin on 150 from a Virgin phone, mobile or landline, or 0345 454 1111 from any other phone to report a fault, or wait here for one of the forum team to pick this up which might be 2 to 3 day's.
When phoning choose the option to report a fault, then ignore all the options offered and you should then be placed into a queue to speak to someone.
