Simultaneous Display and Keyboard/Trackpad Failure

My wife was using her late 2011 13" macbook when the display went black. She plugged in a projector and verified the computer was still working. She found however the trackpad and keyboard no longer worked either. USB keyboards and trackpads do work however. Does anyone know what the root cause for this could be? I'm hoping the logic board is still intact as the thunderbolt display and usb ports are working. We did not purchase the extended warranty and we are just beyond a year now

First question I have to ask.... did your wife spill anything on the machine or drop it? It seems strange that the keyboard and display would go out together. This type of problem is typically caused by spills or drops. (Not saying that's what happened in your case though.)

If the problem wasn't caused by a spill or other accidental user occurrence, take it on in to Apple. They may decide to repair it for free even though the warranty has expired.

Nothing was spilled on it, nor was it dropped. Strangely enough though, it started working again after several hours.

That's even more strange that it began to work again. It may indicate your machine has a loose or binding cable that may be causing an intermittent failure. If it happens again, take it on in to Apple. Apple has been generous in doing out of warranty repairs for free. In any event, you have nothing to lose by taking it to them as all they can do is refuse to repair it for free. Good luck.