Things You'll Need
Instructions
Check the card on the console. Often times, the error message comes up once, but then goes away when the console is booted up again. Power off the console, remove the card, replace it and see if the message repeats. If the message comes back, save any files that aren't corrupted by moving them to another memory card.
Leave the card alone. Place the card away from anything electronic for about a week. The lack of electromagnetic interference could help to fix the card.
Reformat the card. If these steps don't work, the card must be reformatted. This can only be done on a GameCube console. First, all the data on the card must be deleted. After this, restart the console and a little warning should come up at startup. It will ask if the card needs to be formatted. Answer "yes." This reformatted card will work again with both the GameCube and the Wii.