I am running OS X Yosemite 10.10.2 on a MacBook Air 11-inch Early 2014 and my media keys have stopped working. Specifically these are the previous track, play, and next track buttons located on F7, F8 and F9 respectively. It was my belief that since I deleted the 'iTunesHelper' from my Login Items this might be causing it. So, I have placed this back in Login Items and upon a reboot this is still not working. In addition I have tried clearing my PRAM. Anyone have any ideas what else I could try? Thanks.