update - could be the culprit is powerdvd7 ultra - I found this info on another board & it describes my symptoms exactly! - so I may switch to
windvd on the vista PC & see what effect that has:
[quote] "PowerDVD uses their own software codec to decode DVD, Blu-Ray, and
HD-DVD materials. It also decodes and plays DivX and XviD files with it's own built-in codecs. But that also where there are issues. I found that after installing
PowerDVD 7 Ultra, VMC could not play any of my DivX or XviD files. Trying to play using WMP11 (Windows Media Player 11) will produce a "Acquiring Codec" message on the lower left hand corner. However, it would quickly acquire it since WMP11 didn't really need to download it (it's already installed), and the movie would automatically play. Also, on the playlist, the video being played would have a red X as if there was an error, but the movie plays just fine with video and audio.
It's a strange behavior, and no matter what codec I uninstall and try, the behavior is the same. I've tried the official XviD codec and ffdshow, and it's the same thing"[end quote]
whatever, I don't think
DVDfab is at fault at all here.