Ok, my story. I've been using a 300mm AF-s f2.8 on a D300 for 2 months or so. Today, it gives me the fee(nger) warning and won't shoot. I try my 50mm 1.8, no probs whatsoever (ap ring locked like its supposed to be). Put the 300mm on th eD2x(ap ring locked), no probs there either. So I twist the aperture ring and, VOILA, it will shoot on the D300 if its set at f8 or f5.6. So I try an old 28mm AF on the D300. Same deal, fEE if the aperture is locked at f22. But no probs at f8 & f5.6. I'm going to assume its the camera not the lens. But the working at f8 just bugs me. Any insights?