I have 3.1j as well with WiiFree, doesn't work.
Strange thing is that it has japanese text when loading this USA version of Fire Emblem Radiant Dawn.
This seems to have happened on Dewy's adventure as well. Put the USA version of dewy in a NTSC-J Wii and you'll see Jap text and freezes at the start like Fire Emblem.
Is there any way around this? It seems like these games rely on the Wii telling it the language version to load.