I have a M3 Zero card connected to a DS XL, the device was connected to the internet and the DS was upgraded, after this the M3 Zero failed to work saying "an error has occurred". below is the instructions I eventually gathered to fix my issue, I hope it helps:- copy (v4.20) F_CORE.DAT file to root of microSD card. copy M3GUpdaterPlus_450HW.nds file to root of microSD card. copy the (M3Sakura_v1.49_Multi) SYSTEM folder to the root of microSD card. copy a game/games to the microSD, (or a GAMES folder on the microSD). Insert the microSD to the M3Zero device. Flash the M3Zero with the (v4.20) F_CORE.DAT file, by attaching it to the PC with the adaptor/USB cable. Wait for about 30 seconds until the light stops flashing, and remove from PC. Insert the M3Zero device into a unmodified DS, and select the file M3GUpdaterPlus_450HW.nds press select a few times until it completes with message success. restart, and test you can see files on the M3Zero. copy/overwrite (v4.50) F_CORE.DAT file to root of microSD card. Flash the M3Zero with the (v4.50) F_CORE.DAT file, by attaching it to the PC with the adaptor/USB cable. Wait for about 30 seconds until the light stops flashing, and remove from PC. Insert the M3Zero device into a unmodified DS, and select the file M3GUpdaterPlus_450HW.nds press select a few times until it completes with message success. restart, and test you can see files etc on the M3Zero. the M3Zero will now work in your DS that has had an updated firmware.
