Has anyone here heard of this one before? I have the Nikkor 18-200 DX lens (used on a D300), and recently it won't take the picture when the lens is at the 18mm end. It autofocusses, but nothing more happens when I press the shutter button; no picture taken. When the lens is extended even a little, it works fine. I've tried wiping the lens contacts, but no joy. Any idea what might be going on? Something easy to fix?