Is it possible to re-format an SD card on digital camera to salvage photos?

I was using my Canon SD 900 with a 4GB card and hooked it up to my TV to see the pictures. Maybe it irradiated the card,because the card then read, unidentified image, with the photos very small on the screen. These images weren't from another camera card. They weren't edited by a computer.It wasn't an incompatible image. I'm at a loss to retrieve the photos. I guess I'll download first,before doing anything else. Any ideas to retrieve photos without erasing the data? Any help appreciated.