Original post by: Oli ,
It sound like a keyboard fault as if it was anything else then other keys would probably be affected. You could try use keyboard cleaner on it but it would be very hard as the keyboard can't easily be separated from the top case. If you can reseat the ribbon cable as it may have come out partly but it is unlikely. You should boot into safe mode to check its a hardware issue and not a software one as it may save you from having to open up your computer.