I got my Macbook Air last month. It is 2012 model. The problem is When I keep my MBA on a non-flat surface (my lap for instance) and when I keep my hand on the arms rests, i hear a not-so-loud-but-good click sound from the right side arm rest. Have you experienced this before? When you gently press the bottom right corner of the armrest..it makes the sound. It doesn't happen on flat surfaces Its a brand new machine and I don't know what to do. Is this sound natural?