Wii Virtural Console games don't work?

I'm just getting a black screen where I can only hear sound. These only happen with the nes and snes games, the others work fine. These are the things I've tried already:

1.Changed the screen size, 480p, etc.. None of that worked.

2. Deleting my current channels and re-installing them. Same result.

3. Going into the operations menu and and pressing Z+A+2.. I got no sound indicator.

If anyone has any info on this, please help! Thank you!