Do you change another PC to have a try?
Sometimes, the loose connection can cause the undetected problem.
If the consequence is the same, you can use a recovery program to help you.
As I know, this free recovery program is what you are looking for:http://www.squidoo.com/memorycard-recovery
I had used it to recover my photos from my formatted memory card last time.
Never save anything new to this memory card until you have recovered all data.
Always back up your data as much as possible in the future.