If you use the latest firmware (any for Acekard), no Final Fantasy DS games should give you errors or problems. It must be your roms, try them in an emulator. If they don't work there, get some different ones. Did you trim them or anything? Rarely, that can break games. And yes, do format your microSD. But what exactly are the games doing? Black or white screen on boot? Freeze ingame? Error messages? Specifics would help.