Every now and then I need to leave my laptop on overnight to process a several hour video file. The last two times I’ve done so, the screen is black in the morning. The hard drive’s still operating, but no display. Power save/screensavers are disabled, and it doesn’t feel overheated. If I hard reset it, it reboots fine, but I do so blind—I can’t tell if the video is still exporting or not. Any ideas what would cause this display failure?