We own a Nikon D3100 and have had this error now with two separate memory cards within the last month. We will take pictures and they will be showing on the camera preview and then we go to upload them and it says that there are no pictures on the card. After taking it out of the computer we put it back in the camera and it says no images. I have been able to go to a shop and use their data recovery and have retrieved the pictures but it's expensive to do that. Has anyone else had this issue? Am I uploading them incorrectly or is there something wrong with my camera? Thanks.