That is indeed wired. Unfortunatly I don't have access to a Mac to test things. Your best chance are probably filesystem checking tools. Do you (or somebody else reading this) have access to a MAC and linux? The only thing I can think of is that wbfs2fat creates only a single FAT table. By default other FAT formating tools create 2 copys. But using one saves space, is compliant to the FAT spec and the wii FAT drivers ignore (which leads to inconsistencys, which is bad imho) the others anyway To create such an FS under linux use (MIGHT work on OSX too) mkdosfs -F32 -f1 /dev/sdX then check if it works on a Mac can you upload the backup file to let me check for other potential sources?