this problem is not with you disc, I got the same - my lucky is that I bought WII together with friend of mine and we made tests on both consoles, WII Sports with mine WII doesn't work (both copies) on his console they work fine without any little problem! Only one difference is that I got an software update just after I get it from box without testing this game before - of course any other game is working fine too.
So yeah, I am encountering this with two of the five games in bundle (Sports and Party Games) that I won at my job. I brought the game over to my sisters and brought it over to her place, worked without an issue. So thought it was the console, then I see this posting. I exchanged the console and that didn't resolve the issue and exchanged the games. Still to no avail. Not sure where to go from this place. I guess call tech support, sounds like I'm better off calling at home though, when I am by the console and the games.