Yes, this IS a classic case of the SAB problem. I've just discovered the same with my 6 month old X100. Funny thing is, I've probably had the issue for some time but have failed to notice it as I usually shoot wide open. There seem to be many ways in which different people determine whether they have the problem. My method is simple. Switch the camera to AV. Set ISO manually as you normally would for a given scenario. Next take a photo @ f2.0. This will be perfectly exposed. Then take a series of photos working your way down the f stops. As the aperture selected gets smaller the photos become more over-exposed. The camera is selecting a longer shutter speed for the smaller apertures but, because the blades are stuck wide open, this is vastly over exposing the photo. I wonder how many other X100 users out there have the problem but are unaware of it as I was for so long ?