One thing it doesn't seem to like (on my car, at least) is if the drive is not completely empty, but if you have just formatted it to FAT32, it would be anyway.
I guess the next thing I would try is "Update BMW services" (if that's the correct name for the option in iDrive that goes away and checks all of the installed apps).
I guess the next thing I would try is "Update BMW services" (if that's the correct name for the option in iDrive that goes away and checks all of the installed apps).