My MacBook pro occasionally makes this clicking sound periodically. It seems like it happens most during the first few minutes of use; it also happens when I move it. I read this:https://discussions.apple.com/message/22539038#22539038 , because it seemed similar, and someone suggested it being the HDD and being an issue? Is that possible? Mine clicks in about the same spot, but I remember it doing this for quite a while? Is this normal? Should I be concerned? Thanks.