Your DVD player might not support the audio created by the software, which, by default, would be MPEG audio. Are you in the US by any chance? There are DVD players in the US that can play nothing but Dolby Digital/AC3 audio. That's permitted by the standard for DVD player specs in the US, from what I understand. There's no obligatory support for MPEG audio. It's often sufficient cause most (commercial/professional) DVDs feature Dolby Digital sound anyway. Some other players struggle with high bit rates on MPEG audio. So, you might want to go into the MPEG encoder settings when encoding/burning the DVD and change the audio settings. Try MPEG audio with lower bit rates (e.g. 192 kbps or below) or resort to PCM audio. Depending on what program and version you got, creating Dolby Digital audio would be an option.