I've just had the same problem. You need to reformat your memory card (make sure you download your photos first as it will erase everything on the card). Then go into the set-up part of the menu on the camera. In there you should find the option -FRAME NO. This will be set on continuous. Select the option that says RENEW. This will reset the frame number counter. Once you have done this go back into the FRAME NO menu and set it back to continous. You can now start taking photos again as the counter has been reset.
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I've just had the same problem. You need to reformat your memory card (make sure you download your photos first as it will erase everything on the card). Then go into the set-up part of the menu on the camera. In there you should find the option -FRAME NO. This will be set on continuous. Select the option that says RENEW. This will reset the frame number counter. Once you have done this go back into the FRAME NO menu and set it back to continous. You can now start taking photos again as the counter has been reset.