When starting up my 3DS it froze on the homescreen, after testing out stuff i found out that it worked when i didn't have the SD card in, so i tried it in my computer and the same thing happened. i was unable to read the card then it appeared with the message:
To use drive please format
SO basically i've just lost my save for animal crossing and Pokemon X which is really heart breaking. So i'm pretty much doing a replay now.
Really wish this didn't happen to me....