vWii is pickier than original hardware. Do not use standard SaveGame Manager GX. Use SaveGame Manager GX for vWii (special build). Also, ensure your SD card is inserted before you launch vWii mode, otherwise the USB ports drop power.
Understanding Updated Wii Save Files: What They Are and Why They Matter wii save files updated
Tools like "Feather" allow you to modify save data (e.g., unlocking all characters in Mario Kart ) before re-uploading to the console. vWii is pickier than original hardware