Yes, Photoshop has a built in currency detector for US and Euro bills. If the bill's size fits within a certain size/resolution, you can't open the image files (as you've found out). I can't remember what version that kicked in (I think it was CS2 or CS3).
Here's an old forum message from 2005
“I still have PS 7 because I occasionally do graphic arts work involving currency images that PSCS refuses to open.”
(It's in a thread about CS2, so I'm not sure if he meant CS2 or was referring to something earlier.)