@flebber
Audio is already DVD compliant (PCM 48kHz). AVStoDVD does not encode it, but it tries to demux audio (using FFMpeg). For some reason FFMpeg fails to demux audio and gives an error (while video demuxing process ends successfully).
It makes no sense to me (in this situation) that QuEnc works instead Wavi+Aften do not, because none of them are used...
Since FFmpeg fails to demux, I suggest you to set AVStoDVD to re-encode audio to AC3 (use 256 kbps if you want to preserve quality).
@katzenjoghurt
take a look at this
thread about Tool for changing preferred DirectShow filters in Windows 7.
Bye