It is my experience now with a D7000 and the AF-S f1.4 50mm lens that if I have the dial set at "P" and Auto ISO set at 400-6400 shutter 1/100, that the P does not seem to work like my previous camera, a D200. The P setting is supposed to allow you to choose a set of equivalent expose settings by rotating the main dial. However, *all* the choices are at f1.4. I am shooting pictures of a band in a bar, with weird spot lights, but I can not get P mode to choose anything except f1.4 unless I either turn off Auto ISO or set it to min=max=6400. If I use AutoISO min=max=6400, and min shutter speed of 1/60, then the P mode chooses modes with different shutter speeds and f stops.
This did not happen with my old D200, but perhaps as the max ISO of the D200 Auto was 1600, I avoided the problem.