To me that sounds like the hard drive is starting to fail. Although you haven't had it long the device could have got a sudden shock at some point during the transportation process.
I would certainly contact Virgin Media and report this as they will be able to provide you with a replacement. Any recordings you have set up though will not transfer over to the new device, but hopefully as you have only had it a week that shouldn't be too much of a problem.
It will continue working but it is only a matter of time before it will fail, and it is better to get it replaced now than when it is full of recordings that you would end up losing.
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