I know this thread is so old that the poster must have restored his data back. But, I still want to share my stories with you.
Several days ago, my SD card also got similar strange problems. After plunging it to my computer via a card Reader, all the inner pictures became inaccessible, for the computer always gave me a message that was asking me to format it. As we all know, the formatting would erase everything.
So, in order to access my pictures again, I had done much researching over the internet and finally tried many memory card data recovery freeware online. They all worked efficiently on my card.
But, only one memory card data recovery freeware called iCare Data Recovery Free had eventually restored every needed picture and allowed me to preview these retrieved pictures before backing them up. It was really great and worth a shot.
Thank you for your reading.
I hope my word could help others, too.