I had this happen once. What I did to fix it was I loaded up the latest version of Nintendont and ran and played a game for a little bit. Then I downloaded the mod version and placed it in the Nintendont folder overwriting what was in there and started it up and everything worked fine. See if that works for you.
No. I even downloaded the mysterio version via the updates section in nintendont and it worked for just that one time.
Anyway, is there, or can someone make, a bios like myserio's that uses the Triforce bios instead of the GameCube bios?