Before they came out with the later firmware that support exFAT, I had to use (can't remember) some software to format the 64GB card to FAT32. Then, when I went from 3.0 to 3.3, and had more lockups, I've formatted the card through the X3 itself. Prior before ever updating the firmware, I either used a 32GB card (given it to a friend for his camera) and or somehow formatted my 64GB cards into FAT32 (which I don't understand why I can't do that now; maybe because I'm connected through USB; I'll have to use my SP2 as I don't have a converter on me).
Is it more than a year?
Now the X3 doens't even recognize the card for some reason and reverted back to 3.0 (probably why it doesn't recognize it as it's now in exFAT). I'll look into finding a link to their downloads specific to the X3; it seems like FiiO just jumbles all their firmware updates for all their players together.