Sorry that I missed this thread altogether and didn't contribute. Friend, I don't know how low ambient light is for you but I could get a "Gd" from my D40 at shutter of 1/5, ISO of 800 and aperture of F/4.5 with my 18-70mm and I could also do it with my Tamron 17-50mm.
What I did was, I pointed my finger at the white piece of paper so that the camera would focus and read off from my finger at the paper. Then I remove my finger for the final shot.
I wonder if it is the camera contacts with lens that is not able to get information from the camera? I could be totally wrong here, just throwing out some thoughts.