I have'nt had any problems with the sound so far (I work with Windows only).
How about if you add a display that shows the amount of time needed for one frame and the fps. If that stays the same then there must be something wrong with the music, (maybee youzr song?), if the framerate get's less, then you might be creating more and more data without deleting it (ex. A list that get's bigger with the "list.Add(Object Object)" methode).
Valandur