Howdy! Today I left my MBP on without the Power Adapter for calibration. Three hours later, when I arrived home, I found it with a black screen, unresponsive (didn't respond to any key or mouse movement whatsoever). No, the battery wasn't empty of charge, it still had half the charge! This is the second time this happens to me, I can't seem to think of a reason for this to happen. I believe JDownloader was open, but not doing any downloads, but I'm not sure whether it was open or not, but besides it, nothing else was open. Any thoughts?