Some VC gets screwy with 480p. Here's a solution.
1. Change the tv settings in the Wii settings menu to 480i (don't worry this is just temporary)
2. Start a VC game. and hit the home button after 30 seconds or so.
3. Select operations manual and the connect a nunchuck to the wiimote.
4. Now hold down A and 2 at the same time on the wiimote and z on the nunchuck. You should here a chime.
5. Exit the operations manual and all should be fine. Now switch your tv settings back to 480p.