Just realised this during the past couple of days. Recently when having my MacBook Pro placed on a desk and resting my palms somewhat firmly, upon raising my palm I hear a creaking noise. It's hard to describe. Similar to the sound of metal expanding due to different temperatures. Is this a problem with the chassis of the MacBook Pro or does it have to do with the rubber feet at the bottom of the machine? Any of you encountered any strange and unexpected noised on your Mac?