I was having similar problems at one time. I was stopping at my Game Cameras and putting my cards in a Panosonic camera to take a look at them out in the field. Than I would erase and put the card back in the Game Camera. Following those actions, I would have a card that was messed up. Stopped that practice and reformatted my cards. Now I just switch out cards and view on my computer at home. Never had any problems since. When I called Moultrie about it, they said that was very common.