I just ran a roll of "purchased at a drug store" Kodak 400TX with the result from the lab being that film was not exposed. I checked the camera to verify that the shutter was actually firing - it is. Camera is a range finder, so nothing in the path between shutter and film. Maybe I failed to load properly and the film never actually advanced - that's my guess. Is it possible that film which had not had good environmental storage could have all the exposure sensitivity "leach out"? I've still got a couple of rolls, so I don't want to waste opportunity if bad film has the potential of being the culprit.