I have a similar problem: My Panasonic SD card 256MB stopped working with an "Unable to use card" error message in my KONICA MINOLTA Dimage x50 camera.
Another SD card works fine, so it is not the camera.
I tried all kinds of recofvery programs to no avail. I finally reformatted thru my camera, but I still get the error message. My PC cannot see the removable drive E.
I would like to
1) recover my images.
If that is not possible,
2) reformat and reuse my card from scratch.