I have an iMac with a SuperDrive. I've noticed this noise once and a while coming from the drive while it's reading, especially with DVDs. Normally, I'll be able to reproduce the noise by running a DVD video disc in DVD player. Once I select a chapter, I hear a loud clunk from inside the drive. It seems to coincide with changes in reading patterns. Is this normal behavior? Does anyone else have this same event happen to their SuperDrive? I've speculated it might be braking, because I haven't always noticed the problem. But then again, I'm not sure.