I am using a Cannon EOS XTI and I just bought a San Disk 4gb Ultra card. I used the card in the camera and all worked fine. I can view pictures etc, I took the card out and put it in my SanDisk Imagemate CF reader and now I cant see any images. All I get is card access errors. My Mac cant even see it at all. I put the card back in the camera and it says I have a CF card access error and replace the card. I did try a new card again and the same thing again. Another dead card. Any suggestions would be great.