Nvidia GeForce3 & SoundSticks: DVD sound conflict?

"I received a new 733MHz G4 with Super Drive and GeForce3 video card this past Tuesday. Everything was fine until I tried out a DVD. I use the Harman Kardon SoundSticks that I previously used with a G4 450. When playing the DVD, the pitch wavers and I hear a popping, crackling sound. The audio is also fine when I first start the DVD or when playing the music from the DVD menu. It's only when I hit play to start the movie that the audio problem surfaces. Audio is fine through the SoundSticks using iTunes, and its fine through the SoundSticks playing an audio CD on the SuperDrive. It is also fine when playing the DVD through the G4's built-in speaker when the SoundSticks powered off."