I have had a Promethean touch screen in my classroom for a couple of months now and have not had any problems using it. But...yesterday when I turned it on after the weekend, the screen looked totally different. In the top left corner it says "no SIM card" and the entire screen looks more like a cell phone screen rather than a notebook/computer screen. Also, it is all of a sudden asking for a locked screen code. I have never seen this before, nor was I given a code to unlock. Any help and suggestions would be greatly appreciated!