BEWARE SPECK SEETHRU CASES DAMAGE YOUR MACBOOK PRO

It could be the black plastic casing that covers the hinge. On old powerbooks the casing was aluminium and screwed into place, but on these unibody macs the cover for the hinge is just snap in place plastic and can easily be moved out of position - if it's not in the centre of the hinge, the plastic can make this snapping sound.

It's the black plastic directly under where it says 'macbook pro', extending around the hinge to the back of the machine. On the back, you should be able to get a finger nail under one end and you can push it back into the centre. Otherwise with the screen upright use something that isn't sharp or metal, that you can use to slide the casing back.

The only damage issues I've heard with these sorts of cases is to do with trapped dust that ends up rubbing against the metallic coating.

Please don't post "BEWARES" when you do not know all the facts. Do some research before you jump.