Memory card data won't show on computer

Hi, for some reason suddenly, my computer recognises my camera's SD card, but the folder called DCIM (i think though it may have been MISC) that normally contains all the folders with images in is empty, though the pictures are showing up on the camera, and they're definately on the card, not on the camera memory. Also last time I uploaded them from the card, I noticed they had appeared in a folder called nikon 103, and there were 3 folders, 101, 102 and 103, whereas before there was just 101 and 102, and they normally appeared in 102. Hope that makes sense.... please help! Cheers.