The file format for an attached file to a comment is something like:
site/comments/13/abc1d35d277b80364fdc10a3d985c870

I would think that it should be something like:
site/comments/13/P1040922.jpg

It seems like it's just stripped format from the file extension type (name wise). When I add ".jpg" to the file name, it displays like a normal file on my computer.