Some quick thoughts... I dont use lightroom so bear with me... but when you pull the card from the camera into a card reader, do you physically see all the extra files? Are the file size roughly identical to the prior ones? If the files are dead/bad/corrupt, you may be able to see a file size noticeable difference of maybe half the size or even no size. It may be a bug with lightroom being able to handle extra files from that much. Also are you OPENING ALL the files at once or just storing in a catalog/library? If so it may be your computer is maxing out on memory and not able to open the files... If it's just transferring files from the card to the computer, nothing else nothing more, then I'd be worried. Lastly, try dragging the files from your card to your computer... if there's a problem, the computer may either not copy or copy with no info... Give that a try and let us know.