I couldn't get audio in my final movie so I started a new project as a test. I just added one video track and one audio track. I chose the Save it to my hard drive option and the final video has no audio.
(former)Cornico, if you give DVD Architect a file rendered with the PS template (video+audio), doesn't it get recompressed? "DVD Architect friendly" templates (separate video and audio) are recommended, if you go to DVD Arch., as you know.
And try to get in touch with the mods. They should be able to help you be (current)Cornico again ;)
You should be rendering a video-only MPEG2 file with no audio, then separately rendering an AC3 audio file. This is the most compatible format and is what DVDArchitect is expecting. The audio you get when you select it in the MPEG2 advanced template is inferior quality, and not necessary compatible with all DVD players.