Im new to Macs and I recently made the wise decision of coming over to the Mac side of things. Got a new 13" MBP and love it. Im sure I could probably find this answer somewhere on the web but don't feel like searching. But why can I sometimes adjust the backlit keys (F5/F6) yet sometimes it won't let me turn them on or adjust anything? Does this have to do with the lighting or time of day? Thanks in advance...