I seem to have the same issue.
New card, installed and worked. Tested by mving a couple of pics
Loaded up the card over two weeks.
Inserted into reader - not recognised: drive needs formatting!
Put back in camera..all pix visible..
Connected via cable..format message again. Pix still visible in camera.
Tried different reader. format message.
I MAY have put the sandisk card in the other reader BEFORE trying to read it which MAY have corrupted the files sytem if other posts are correct.
Which is a bit stupid...
Waiting for support to come up with an answer. Any body got any ideas about how one might get pics off except by one at a time through the camera memory...