Bought this tv a couple of weeks ago and connected an external hard disc for recording. The problem is that after a couple of minutes the tv loses connection with the USB drive and we have to unplug and re-plug the USB device again. Is this normal for this tv? At the shop they suggested to get a USB drive that can be connected to the mains but weren't 100% sure this would solve the problem. I also read about people using USB sticks but perhaps this was to watch movies they got from the web. Any suggestions please? Thank you...