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Question: DSC-S980 steady-shot sony

I took a picture and turn the camera off. A few minutes later I turned the camera back on to take another picture and this appeared: Reinsert the memory stick." I did and I cannot view the 100 or so christmas and vacation pictures of my children. I also cannot take pictures. This happened out of nowhere. Is there something I can do to view or retrieve this priceless pictures or is the card defective? What should I do or try now to get my pictures? Thanks so much!