For some reason, consoles which ran all other games fine had trouble reading Super Smash Bros. Brawl's DVD disc.
Nintendo investigated the matter and found out that "Super Smash Bros. Brawl utilizes a double-layer disc which has a large memory capacity. A very small percentage of Wii consoles may have trouble consistently reading data off this large capacity disc if there is some contamination on the lens of the disc drive."
So, what caused this "lens contamination"? According to the Boston Herald, second hand smoking is the culprit.
Some Wii owners took the matter into their own hands and managed to clean their consoles' lenses by blowing compressed air into the disc drive, but Nintendo advises against that. " Nintendo has specialized cleaning equipment that can resolve this problem. (Please do NOT attempt to clean the lens yourself, as you may damage the system)", Nintendo's support page states.
