I just bought a new 13 inch macbook pro. While i was calibrating the battery i heard a slight click....I thought it was just me at the time and didn't think anything of it. I heard it again 10 minutes later. I am now hearing it when i use the machine very, very quit, and not totally consistent with time or anything else. Just got this machine on Thursday morning. Suggestions? Is this machine ok, or should I bring it back tot he store I purchased it from? Suggestions? Thanks.