DVDFatal is when a Wii or GameCube has a fatal error when loading a disc that the console cannot recover from. DVDFatal is what the function is called in the game code.
When a DVDFatal happens on a Wii, an error saying something like "An error occurred. Press the Eject button, remove the Game Disc, and turn off the power to the console. Please refer to the Wii Operations Manual for help troubleshooting", and the only way to get rid of it is to power off the console.