How can I configure my keyboard to be backlit at the login screen? I recently had to reinstall Lion.  Now, when I boot the keyboard is not backlit when at the login screen.  It used to be backlit when at the login screen.  

I'm using a Macbook Air 11" July 2011 model.  In System Preferences I have the checkbox: Automatically illuminate keyboard in low light checked.  The setting for Turn off when computer is not used for: is set at Never.
It appears that the problem is related to FileVault.  When I turned FileVault off and rebooted in safe mode the problem went away.  I could change the brightness of the screen and the keyboard at the login screen.  Volume controls worked too.  Now that I've turned FileVault back on the problem is back.