Are you loading the emulators from your Wii U menu using a forwarder? If that is the case, then loading the programs that way disables vWii from seeing any USB device. Its one of the tradeoffs you take when using it in that process. I have no idea what voo-doo that USB loader GX is doing to make that work, but it works and I don't ask questions. I have a large SD card in my Wii U and load things from there.