Sounds like your box is faulty, you can try doing a factory reset to see if that helps, you can select the option to keep your recordings if you have any, or select option 2 which will reformat the hard drive.
If or when the box deletes everything again then you will need to call Virgin on 150 from a Virgin phone, either mobile or landline, or 0345 454 1111 from any other phone to report a fault, or you can wait for a forum team member to pick this up which can be a few days.
