My MBP was in sleep mode since this morning, and when I opened the screen about 4 hours later the display would not come on. I tried pressing some keys and move the trackpad, no luck. I then did a reboot by holding down the power button. I heard the Mac startup sound, and my keyboard liteup. Still no display. Not even the Apple logo on the back of the screen lights up. Any ideas what may be causing this? My first though is a possible graphics card failure, but I read some other places that people have issues with the MBP not coming back out of sleep.