Hey Late 2008 MBP Owners... I tend to use my MBP in bed a lot, propped up on my thighs at about a 45º angle, and I've noticed a grinding noise from the fans when using it this way. I've just learned that this grinding noise is not a result of case compression, as even if I lift the machine up by the sides and rotate it fore and aft in space, there's a 10º zone (between 40º and 50º approximately) that the fans make a distinct grinding sound. Note that, for me anyway, this will only happen between minimum fan speed (1990 rpm) and ~2300. Let me know what you guys find. Be sure to put one ear a few inches away from the hinge area when you test!