Had this happen to me on as well. i tried lense cleaner from Ninty and no change. song would start looping or become off sync but finish, then lock up and error message. verified 3 burns with ImgBurn, all failed. i tried TY, Verbatim, Memorex, and Princo media.
Because of the way this game is made, there are near-constant reads from the wii disc, if at any point your laser assembly or disc cant keep up, error.
my solution was to load it up with USB loader and forget about trying to get it to work off a disc. i probably could have tried a few different burners with Verbatim and TY media, but why waste the media when a 4gb usb stick will work flawlessly.
sory i couldnt offer the solution you were looking for man. try it on someone elses softmod wii and see if you get the same results? i tried on hardmod wiikey1 and softmod gamme/softchip, no changes.