Originally Posted by Delphinus
Probably your card has a corrupted file system. Unfortunately the preview of the image in the camera canít guaranty that the file is OK.
I recommend that you make a full copy of the card and then that you use a program to verify and correct it and after make another copy with your fingers crossed.
Finally with your camera make a full format of the card.
Dont foramt the card until you have recovered the images as otherwise getting anything back will be almost impossable.