That is a disc reading related issue. On my retail disc I get a significant amount of studdering. Running off HD the problem is gone. They did a bad job optimizing their streaming code and didn't allow for the slow(ish) Wii DVD reader to catch up. It really is a bummer to, for some it seriously hurt the game. For me it was more of a minor annoyance but still.
XBL: WiiVault Wii: PM me PSN: WiiVault
PC: AMD Athlon II Quadcore 635 (OC to 4.0ghz) , ATI Radeon 5770 1GB (x2)
MacBook Pro C2D 2.8ghz, 9600m GT 512 iMac: C2D 2.0, X2600XT 256