Top row of keyboard isn't working I just turned on my Macbook air this morning and now the top keys aren't doing anything (F1, F2, etc). I can't turn down my keyboard light or anything. I tried going to system preferences and checking "Use all F1, F2, etc keys.." option but I am still not able to do anything like turn down volume or anything. I am using OS X Yosemite Version 10.10.1 .
This happened to me a while back... First, try just holding down the power button for 10 seconds, to force the MacBook to shut down, and then reboot it normally. That sometimes works.  

Failing that, you could try resetting the SMC:

Resetting the SMC on portables with a battery you should not remove on your own

Note: Portable computers that have a battery you should not remove on your own include MacBook Pro (Early 2009) and later, all models of MacBook Air, and MacBook (Late 2009).


Shut down the computer.
Plug in the MagSafe power adapter to a power source, connecting it
to the Mac if its not already connected.
On the built-in keyboard, press the (left side) Shift-Control-Option
keys and the power button at the same time.
Release all the keys and the power button at the same time.
Press the power button to turn on the computer.

Note: The LED on the MagSafe power adapter may change states or temporarily turn off when you reset the SMC.


Source: Intel-based Macs: Resetting the System Management Controller (SMC)