Get yourself a USB reader, or a Notebook and PCMCIA adaptor, and test the card.
Also, try formatting it in a camera. . . Apparently that should work according to tomeone who rescued theirs that way. But first, try the card on a PC. If you can write files, then read them again after unplugging, replugging, it's not the card. . . Maybe they're just not compatible? My Kingston 256 works though. . .