I have a new white unibody macbook, the ones that were released on october of 2009. The first day i got it, it was solid as a rock. I could pick it up from anywhere it was completely silent. It made no creaking noises whatsoever. However now that i have had it for at least half a week, the bottom plate makes a creaking noises whenever i push on it in the middle. Should i be worried or is it normal? Right now its nothing major but the noise is annoying because it will sound whenever i put it on my lap. What should I do???