Some old laptop computers by Sony may not accurately read any SD card larger than 256-k or 512-k capacity.
Many older card readers may not accurately read any SD card larger than 2 meg.
An SD card with a capicity over 2 meg needs a card reader for SDHC (high capacity).
Things to try:
Read the card with someone else's computer.
Try another card
PC or Apple computer.
Capacity of SD card.
Brand name of the card.
Was the card formatted by the Camera (not the computer).
Was the card used in another device.