I'm with Eric there Karl. As you know, I have the same camera, although I might have a different card. It certainly sounds like a card problem, not the camera itself. Normally, I just download straight to the computer from the camera, and then, after checking the download was successful, erase from the camera. I don't normally format each time, unless I've removed the card for some reason, but I do re-format now and then, just to ensure all is working OK
Also, always ensure the security 'tab' on the card is in the correct position, and fully in place, as this can cause read errors, and lost images otherwise.