Are you sure these are genuine cards? Many counterfeits exist which pretend to be much larger sizes than they actually are. Grab yourself a diagnostic tool designed for flash memory and confirm the specs. Could it also be that they are genuine but are very slow, thus failing to allow the 3ds to read the game quickly enough when the rom is large? What class are the cards?with the generic 2GB works fine, just these 4gb are problematic
no solutions?