I'm so sorry to revive this supposedly long-dead thread, but I'm having trouble getting this to work.
I'm using Nintendont with the modified Bonus Disc ISO on a USB device (FAT32), using a physical GC Memory Card.
Pretty much the only option left "on" on Nintendont is Native Control.
Still, everytime I run the ISO, it says "Pokémon Colosseum save data not found on Memory Card in Slot A!" (in japanese, of course).
It has an US Pokémon Colosseum save data, with all 48 Shadow Pokémon purified, AND an open slot in the party, so I don't think the save itself is the issue.
Can anyone help me out? Do I need a memcard with Japanese game saves?