Hi, After a long wait I finally received my Nikon 24-70/2.8 however I noticed that while focusing it makes a crackling sound. The sound is not very loud but it almost seems like a lens with VR trying to stabilize. My 18-200 sounds much quieter than 24-70. Did I get a bad copy of the lens? Anyone else experience this? http://www.youtube.com/watch?v=HTdv5DGZLs8 Thank you for your response.