I just developed 2 rolls of film from my RB67 that came out completely blank. I have no idea how that happened. Luckily I can reshoot, but it's pretty alarming. The edge markings are developed and I just used the developer to develop some negatives within the last week, so I don't think the developer died on me. I didn't put the fix in first, because the edge markings are there. I'm not an expert with the RB67 but I've shot a few rolls through it since I got it. The camera has been sitting for a while, but it worked last I used it. I didn't leave the dark slide in, because I remember taking it out and the RB won't fire with the darkslide in anyway. It was slightly overcast weather so I don't think I could have underexposed that much even if I tried--it's 400 speed film and the camera only goes up to 1/250th of a second and f/32. I suppose the only explanation is that the lens shutter did not fire. Any other ideas?