Hi guys,
Thanks for your enthusiastic responses.
Unfortunately none of them worked.
I have latest FFDSHOW (not tryouts, not sure what they are).
Microsoft Audio Decoder did not work, neither did FFDSHOW Video Decoder with settings as recommended.
It's puzzling because DVDs play PERFECTLY in Windows Media Center.
I've got a feeling it may have something to do with the audio settings. I have my HTPC connected to a DAC via optical toslink. The DAC is only a stereo DAC, a doesn't decode AC3, so I need to send it PCM 2 channel.
The DVDs wouldn't play in MC15 unless I selected LPCM in FFDSHOW audio settings. I'm not sure if I should select analogue audio or digital 2 channel in the video audio settings, because I believe that analogue audio should be used even if using a digital connection if you want uncompressed (ie PCM). Anyway, selecting digital 2 channel doesn't fix the problem.
Still think there may be a clash somewhere in the audio settings...
Ben