Did you ever take that card out while your camera was still turned on? I did that once and it corrupted my card. I was able to have the camera store do what they do best and they did recover the files but it took a while (a couple days). The store replaced my card for free!!

I may have done at some point, but I think it got corrupted as there was viruses and trojans planted into my laptop. It all went funny when I put the card into the side of the laptop. £120 to get my laptop fix, but the store did give me a new, better card.