Just thought i'd share this to see if anyone else has run into this problem. I opened up my MacBook earlier today and found a wonderful surprise! It seems as though the groove in the casing near the screen has cracked the side of the casing that it closes down on. I have AppleCare but i have a feeling they're going to call it my fault and charge me a lot to fix it. I'll keep you posted on what happens.
i think this groove is what caused the crack
i think this groove is what caused the crack