I was at my desk at work using my MBP. Suddenly, the green LED on the power feed went dark, the screen went black, and the battery charge indicator lights will not illuminate at all. I doubt it's an AC power supply issue, as I was using it in closed clamshell mode and I think it has to have wall power to drive an external display. I'm inclined to suspect a third party battery I installed a year ago (ifixit was the source). I can swap a known good battery into tonight. Any suggestions for things to try before then?