Have you recently viewed that SD card on a computer running Windows Vista? I had
used my card reader on my computer running Linux to get some pics from my
brother's camera downloaded and it worked fine. I then put those pics onto a USB
stick to put them on his laptop with Vista. Worked fine also. Later, I went to
use my USB stick and couldn't delete the pics off of it, nor could I put
anything else on it. Neither Linux or Windows would do it. Was telling my son
about it and he said Vista could have messed it up and talked me through using
Linux terminal gparted to delete the partition on my USB stick and now it works
fine. May work for you, but you will lose the pics and info on your SD card. In
gparted, it showed the volume as FAT 16 and my son had me delete that partion
and set the new to FAT 32. Hope this helps.