I have a new Canon 5ds. Several times last week, I took pictures and they appeared to be saved because (1) it took a time before the red light went off and (2) I got a preview on the screen. But when I got home and tried to download the images onto my computer, there was no new photos on the card. Further, when I tried to view the images in my camera, the new images did not appear. I replaced my SD card but the same thing happenend. Help!