usually if a card is corrupted it won't read at all. Like a 256 xd card I had, put it int the camera, inrecognised asked to reformat and it failed every time... same in PC.
Looks like just the files have been corrupted, not the card..
Format the card IN THE CAMERA and see if it goes back to normal.
SD carrds are quite cheap in the UK now, esp here click here 1gb for £16.49