Do you happen to have a chipped wii?
my friend has one and we tried the american brawl disc and it count not be read. his japanese burned brawl copy could, burned gamecube games could, and so could american wii games. i think my friends problem was the update blocker or whatever was put on his wii when the guy chipped it to prevent the bricking from japanese upgrades.
i went home and it installed a wii system update on my wii and it worked just fine.
if this doesnt help, sorry. i guess u can do whatever they said above