i have the same lens... not sure what you mean by focal length ring (for zooming or focusing?), but the zoom ring turns smoothly regardless it's mounted or not. the focus ring should move freely once the camera is set to manual focus. if it's not mounted the focus ring on the lens should be able turn freely.
Oh... D3K you mean? Maybe he upgraded from D300s to a D3s and kept both bodies. D3s will convert the image to DX format when it detects a DX lens rite? Just that you wont be utilising the sensor fully for optimum image quality. :think: