There is already an active thread on the subject of corrupt memory cards, and how to recover the pictures. Here is a link to that thread:

A precaution...
Anytime you put a new memory card in a camera, you must, must, must format that card using the camera.
This conditions the card to match the camera.

Failure to do that, is like setting a time-bomb.

Using a card reader (like the one on your printer) is OK. But never format the card from the computer. Only format the card using the camera.