There have been tons of problems with SSBB on Wii (it seems mostly those from launch, as mine is) several sites are reporting this and Nintendo seems to be saying them same thing as they have setup a support area for SSBB including a Free and Fast (what they consider fast I don't know) Repair Process of sending them your Wii. I don't know how wide spread this is but it looks like a lot of people are reporting it and Nintendo is also expecting this problem with launch systems.
| Nintendo - Customer Service | Wii - Super Smash Bros. Brawl
I don't have the game yet. I plan to pick it up in a day or two. My Wii is from the midnight launch so we will see if I have any problems. I might go rent it tonight just to check my Wii before buying the game.