If you get a few corrupted memory locations on a card, one image might be affected. It won't happen again until your camera writes to the same memory location.
Do a erase and then total reformat on your computer. Reformatting in the camera does not detect the bad memory block, but a complete erase writing all zeros to every location on the card will detect bad blocks and mark them as bad so they are mapped out.
I use Image Rescue 4 to erase a card. It takes a while, since you are writing to every memory location, and verifying it. Then do a complete format.
Of course, if your memory card is dying, then more bad memory blocks will develop in the future, and you will need to replace it.
