Yeah I had this too, but this is not an error in Homebrew Channel, it probably means that your GPU is damaged. Try playing Wii games, you should see these dots there too (they usually appear only in the far background, e.g. the sky). These "GPU damage dots" are usually black, but in Twilight Princess, they are green and in some channels they produce weird artifacts instead.
Such GPU damage is caused by overheating from leaving WiiConnect24 on in standby mode, and it's quite common. At least that's what Nintendo told me. You should send your Wii to them, they will repair it free of charge, even after your warranty expired. They usually don't notice if you meddled with the system, but you should still uninstall any hacks, channels and cIOSes.
