hi all, sorry if this has been identified already in another thread, but i haven't noticed a thread title yet. for the record, i'm LOVING the new, more powerful 13-inch mac. very, very wonderful. anyway... i have noticed that when the laptop is open and i'm lifting it up, putting it down, or simply moving it, something from inside the machine makes a single click sound. just a single tap and nothing else. it will not happen twice. i'm thinking it might have something to do with disengaging the hd when sudden movement occurs. but, this is just a shot in the dark. any thoughts?