Are you using component cables? Try the "Wii Component Cable Interlace mode"
This is a temporary fix to problems with various Virtual Console games being played over component cable on HDTVs. The mode can be enabled by accessing the operations guide of the game, and (with the Nunchuk attached) pressing the buttons Z + A + 2 simultaneously. A sound is played if the mode is enabled correctly.
Several older games also have updates available to enable the feature. The mode can be disabled by using the same method, but with the button combination Z + A + 1 instead.
Let us know how you go. =)
Metroid Prime Trilogy
24/06/2009 / Final dungeon - Ocarina of Clank