I work in high ed and occassionally see students with this problem. No telling what combo of cameras/cards and home computers they use before they get to our Macs.
I had a bad time with the error as well when I would regularly optimize the external FireWire drive I have images stored on (I also have CD backups; I use the FW for organizing and easy access). I stopped doing the optimizations of that volume and haven't seen the problem since. I think it has something to do with the image header getting chopped or scrambled. If you can access that info and repair it (somehow?), perhaps it would work.
Also on the Mac, I have seen GraphicConverter open parts of corrupt images that
PS wouldn't touch.