Why would you translate your own nickname to other languages lmao, it messes it up. Just leave everything as it is. Also that japanese translation makes even less sense than before.
same issue here. jap. console 4.4.0-10J. tried many things (different cards/filesystems, console/browser settings reset etc.), but haven't found a solution yet.
Japanese console FW 4.4.0-10J
I also found out that going to Nintendo DS Internet settings (or whatever it is called in English FW) resets the exploit and I can enter DS Profile Settings. The name is set to Matthew and the birthdate is 29.05 for some reason (neither is mine).
Still freezes trying to launch MT Launcher at step 10a crashes to Home screen and a prompt appears saying that the system will be rebooted. Did everything exactly as told in your guide, no luck.
I'm also having similar problems. Stuck at step 10a (until then everything goes as it should be it seems), trying to launch DS Profile Settings results in crash and reboot. Tried multiple SD cards (formatted both in FAT and FAT32 just in case) and loaders. Japanese console downgraded to...