I had it only 2 weeks, last night noticed that it makes a buzzing sound. What the hell is it? When I switched IS off it stopped doing it. IS back on, buzzing back on. This is an expensive lens, is it broken, lemon...? It was not like this when I purchased it and I only took it out once to the park for test shooting. What do I do now? Do I need to take it back to the store I purchased it from and do they send it for repair? I am in Northern California, where do they send it, how long does it take and will it function as new afterwards? I am pretty upset. Please help!!!!