I was just going about my normal business (Facebook, e-mail, etc.) this morning when suddenly this appeared: I am unable to use my mouse or keyboard. The fan turned on shortly after this message appeared (unusual), so I closed the Macbook, but so far the fan remains on (20 minutes or so later). I am worried because this message doesn't designate an origination. I'm worried that powering down and then back up again will install malware or something. Any advice? Have you seen this screen before?