Colyn, thanks for the reply. I found a diagram online. If I am not mistaken, the drum ends are at the outboard edges of the shutter, while the inboard edges -- the edges that form the opening -- are attached to something called "laths." If this is correct, then it is the lath that is the problem. The shutter curtain fabric does not appear to have come loose. Rather, the bottom of the lath (if that is the right word) seems to have come unattached from whatever it is that holds it in place and pulls it across the focal plane when the shutter fires. Does this make sense?