I just got my new 13" MacBook Air, but I've noticed something... when moving the computer around, clicking some keys, changing the display angle, ect., the computer makes creaky/crack-like sounds. Not every time, but kinda often during normal use. It's like the body wasn't built 100% solidly, I don't know how else to explain it. Anyone else notice this? *hoping everyone else does so my computer is normal* 