I only have the one DSi XL but am having exactly the problem you describe. I am using 1.4.1E firmware and 1.6.1 core. I tried formatting the card in different ways and putting paper under te contacts etc. etc but no joy. I have tried two seperate M3iCards with the same outcome. If anyone has...
@SylverReZ, I also heard one of the Prince of Persia games was so unfinished that it required the "24/7 online" drm so a puzzle could be done and the game could be finished. And that when the Ubisoft servers were closed the (cracked) game was impossible to finish or something like that
I like that games can be fixed after the fact, hate that it's being abused via beta tests... And DLC... I was a 7800 owner back in the day and loved Impossible Mission, turns out I couldn't beat it because it was actually impossible lol