F5 and F6 keys (MacBook Pro) do not adjust screen brightness after upgrade to OS X Lion

Hi All,

since "upgrading" my MacBook Pro from Snow Leopard to Lion, the F5 and F6 keys for adjusting the monitor brightness do not work anymore! No matter how I set the settings for the monitor, the keys do not work.

Sometimes, the MacBook now just uses a low brightness and the only way to modify this is to open the system settings and change it there.

Does anyone know how to fix this so that it works properly (like in Snow Leopard) ?

Thanks,

Kristian.