iPhone Mute button not working when playing movie

I'm using this code to play an intro movie:

IEnumerator Start() { yield return 0; iPhoneUtils.PlayMovie("GameIntro.m4v", Color.black, iPhoneMovieControlMode.CancelOnTouch);

     Application.LoadLevel("MainMenu"); 
 }

The mute button on the side of the iphone (3G) is not muting the sound in the video. I'm building for the 3.0 OS target. It seems there's a 'ringer volume' and a separate volume for the iPod music.

Please let me know if you know any way to fix this.

If it's not possible directly from Unity, does anyone have a quick code sample to place in an Xcode .mm file, to use MPMoviePlayerController and call it from Unity Advanced, to play the movie file (and work with the mute button on/off) ?

Thanks a lot!