Glad to see it works now, but it's a bit weird. I use a 16GB SDHC card to play Project M, and it seems to work. I also use CFG USB Loader since my Wii can't read dual layered discs anymore, and as far as I can remember, I didn't have to make additional configurations to make that SD card work.
Could it be the SD card format?
I have no idea. My card format is FAT32. Is yours different? I am at a total lo ss here.