Something to consider.

It may have something to do with the maximum capacity of the memory card, and laptop card reader.

Some older laptop SD card readers have a limit of how big a capacity it can handle.
Some have a limit of 512meg, 1gig or 2gig.

If you erase or delete a file on the card by using the computer, you can sometimes scramble the card/camera file information. You should only delete files by using the camera. The same can happen if you put files onto the card with the computer.

And; as always, rule number one is: for best performance you must format a new card with the camera before taking pictures.