Since Friday my sky+ box has been unresponding to remote or push button access. I have to reboot it constantly, after which point it works perfectly, but, what seemed like a one-off, is now having to be done all the time. Pressing any button has no effect - I can't change channel or access any menus, although you can continue to watch the current programme perfectly. Unit is about 2 years old. Does the hard disk need replacing, or is it something more serious? Hard disk is the original one supplied. Have also had a few failed recordings lately. thanks.