I just tried burning a GameCube game to a Verbatim DVD-R. I burned at 2.4x with ImgBurn, installed version 4 with launcher of the cmios... and whether I use NeoGamma or GCBackupLauncher, the Wii's drive will just sit there trying to read the disc, making odd little noises that repeat endlessly until I turn it off. The disc was verified after burning.
Really don't know what I'm doing wrong here. I have a launch unit Wii if that means anything.