Yep, it's a faulty head unit. It happened to mine over Christmas.
I phoned the dealers about it and they have changed it under warranty without hesitation. Apparently it's a common fault. Be careful because when it goes into a "frozen" state it can drain the battery if your car doesn't get used much.
You can get it working again though as a short term fix, if you disconnect the battery for a while it resets the head unit and you just have to put the code in for it to work again but it is a short term remedy.
Sorry to be the bringer of bad news!