So I'm getting the exact same issue as in this video or pretty much about the same problem as this thread only a little worse. I just got this in the mail today, and it worked once or twice, though first time only tested to see if the card would actually work and hence didn't install the firmware. 2nd time around I did install the firmware but I didn't format it before installation so I got a FAT error once I tried booting a game. After I formatted it, put everything where it should be and was ready to go, it just started freezing at Health Screen. As demonstrated in the video, it's not the microSD that's the problem, as the same thing happens whether I have the microSD in or not. I tried all the paper tricks I could (minus the last one, since I'm using a DS Phat) but to no avail. Not sure what I should do but to ask for a replacement. I know my DS Phat isn't the problem, as Retail Games still work. As a little bit of history though I had an M3DS Real that used to work but alas has died I guess. I have no other DS to test on.