I've formatted and upgraded with 4.3i firmware several times but most roms freeze up on a white or black screen when I try to play them. It was working great a bit ago but I went a month without using it and now its like this.
1) Format the card and put everything back on 2) Use a thin piece of card or folded paper to ensure a good contact between the DS and the M3 contacts (this happened on both my M3's)