Problem with Z-5500 and some AVIs w/ no vocals

I’m having an issue with my speakers playing certain AVI files. I’ve noticed that all AVI files ripped at 1.4g don’t have vocals, they have background music but no vocals. My 700mb movies play just fine. If I rip the same movie with the exact same settings, one at 700mb and the other at 1.4g, the 700mb one works and the 1.4g one does not.

I am ripping using AutoGK 2.55. XVID and MP3 (default settings).

I have the Logitech Z-5500 speakers connected to a Creative X-fi Titanium with analog cables.

Any ideas?