VOB to AVI - Very strange loss of audio

[Bully9]

I've been recording a TV series on my DVD recorder and archiving to avi using my computer. The first 6 episodes worked fine, but now i have a really odd problem. The dvd disk produced by the recorder plays fine in the recorder itself, but produces no sound when played on my PC - unlike all previous episodes. Other DVDs- homeburnt and shopbought- work fine. Mediainfo Virtualdub Gspot all recognise AC3 audio in the vob, say codecs are installed etc, and i can copy the VOB onto my hard drive - still no sound. Has anyone any idea what the problem is please?

[Baldrick]

are you just playing the vob? tried demultipex/split out the audio from vob using for example pgcdemux(from the dvd) or tmpgenc (under file mpeg tools) and then play the ac3 file.
have you tried convert to avi? no sound then either? how do you convert?

[Bully9]

Hi Baldrick - i've tried playing the vob only or the recorded dvd in powerdvd, wmp and wmpclassic. No sound in any app. I tried to demux in DGIndex and the app crashed. I've just dropped one of the vobs into goldwave and it does save a stereo wav file, but one channel is a flat line and the other has some "sound graphics" but no sound comes out of the speakers when i play it in gwave or wmp. Tmpegenc says invalid mpeg file if i try to demux the vob. Virtualdub converts to avi no problem, but no audio. Weird.

[Bully9]

If i look at Audio codec properties in Device Manager, it lists 17. If i double-click AC-3 ACM decompressor (or indeed any other codec) and then click OK to return to the list, i now have only 13 codecs showing. The AC-3 decompressor is one of those that disappear. If i start the process from device manager again, all 17 reappear. It's the bottom 4 that disappear - Windows media audio, AC-3 ACM decompressor, Voxware compression toolkit and OGG vorbis audio codec. This shouldn't happen, surely?