I was on my 13" 2010mbp, which I've had for less than 3 weeks. I was checking some mails, watching some streaming videos, then i hear a whirring noise and my mac just turned off!. Currently using an external monitor/keyboard/mouse. At first i thought the power went out, but realized the external monitor turned on the 'sleep mode' light on. The charger connected to my mac was still showing orange for charging. What just happened there! Should I be worried? (I know for a fact that software update didn't restart my computer because I'm updating now, and because I received no notification warning prompting restart.