I suggest getting Wii SAve file manager GX http://wiibrew.org/wiki/SaveGame_Manager_GX . If that doesn't work, I don't know. Try having a SD card lower than 4gb, and have the disc in before you start the app


Also, you might need cIOS 249, which you can get from here.

http://wiibrew.org/wiki/CIOS_Patchmii_Installer