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.
Ive noticed that after i take out my sd card and put it in my laptop to copy pics to my laptop , some files show "file error" after i've put the sd card back in my camera. They can still be seen if i put the sd card back in my laptop but not no longer on the camera. Its not all the files just random files. Why is that?