I loaded a roll of 24 exp. C-41 B&W (yeah, I know) into the (1962 vintage) Voigtlander and headed downtown to do some afternoon shooting. At first, everything was fine, and the rewind knob unspooled normally as I advanced the film for each shot. Then, on about the 10th or 12th frame, I started getting an odd feel as I tried to advance the film and the rewind knob stopped moving. I rewound the knob to take up any slack, but that didn't make any difference (there really was no slack). When I got to where the end of the film should have been, it didn't end, and when I rewound it, it only felt like about 10 frames. So, obviously, it had stopped transporting. It appears that the film leader became detached from the take-up spool. I have had this happen at the very beginning of a roll, but never half way through it. Strange. I have loaded another roll and everything appears normal, at least for now. I should add that I've had the camera for 30+ years, though I have not used it much recently. I did finish a roll just last week with no problems. This is obviously not something that I wish to have happen again. I'll find out what the film looks like tomorrow. I've probably got 10 frames with a multi-multi-multi-exposure 11th! Any thoughts as to why this might have occurred?