MPEG-4 won't play???

This isn't exactly an iMovie question, but it does have to do with video, so I thought this would be a good place for it.

I have several short MPEG-4 video clips I got from a friend. When I clicked on them to play them, one at a time, I got an error message saying that "The document could not be opened. The movie's file format is not recognized."

That was confusing, since it says on the thumbnail on my desktop in big letters that it's an MPEG-4 with the QuickTime logo underneath.

I wen to Get Info and there wasn't much more information there: "Kind: MPEG-4 movie"; "Size: 193 KB on disk" and when it was created. It also says that I should be able to open it with QuickTime.

In the past, I've used MPEG Streamclip to fix problem videos, but when I tried it here, even Streamclip couldn't open it. I also tried faasoft converter, and that didn't recognize the file, either. I also tried to import into iMovie, but again, no dice.

The only other bit of information is that I know when my friend took these movies, he was using a camera meant usually for taking still photos; it also has a video capability, and that's what he used to record these MPEG-4s that I got from him.

Any idea of what's going on here and how to fix it? Thanks for your help.