try cleaning the disk
It's not a disc, it's a channel.
@op: Try removing it from the system menu and reinstall it from the disc? Did you patch any of your IOS slots below 200?
I don't have a disk, I'm playing from hardisk, is it the same?
Or should I use .wad installer for it?
About the IOS slot below 200 I'm not remember, must check it first.
But I don't have problem with other games.
No you can install it from the WAD that's on the disc image but I'm not sure how to extract it. However, there is no way to launch the game from USB with the channel. You'll still have to go through a loader to do that.
I think I've seen someone shared that .wad online, I'll try to find it again.
But the channel isn't for launching the game from disc nor USB, it's to launch simlyfied version of wiifit that can run without CD (just for daily body test).