Canon Rebel XT EOS 350D “CF err”

I put a CF card into my Canon camera and got the message “CF err” (compact flash card error). Web searches yielded frightening diagnoses of bent pins. Instead, it turned out that the CF had been formatted with FAT32, but needed to be FAT for the camera to recognize it. When I reformatted the card, the problem went away. (They had become FAT32 formatted because another device in which I used the cards reformatted them automatically.)