Wii problem

[Azure-Tranquility]

Odd... maybe the data side of the ssbm disc was scratched at the part where it stores data for Single Player. Thus, that is why the disc cannot be read.

Either get it re-surfaced, or if that doesn't work I hate to say it... but either stick to multiplayer exclusively or order a new copy. You CAN unlock all the characters by doing VS Matches btw, it takes a LONG time but it's possible.