I've tried the various settings and only get results I originally reported (above). That is, audio but no video, or video but no audio. I have DirectX 10 installed (Vista Ultimate).
No idea, but in versions prior to 5.2.x I DID have both audio and video working in Preview. It's only in the past few versions that the combo ceased to work.
The card is an ATI Radeon X600 that came with my new Dell in Oct. 2006. (Yes, I know it was defunct at the time, but it was the more powerful of the two choices that Dell ALLOWED one to purchase with the system.)
When I started having problems, I updated the card's driver and the version of Catalyst (both dated early Dec. 2008). When that made no difference, I rolled back to the previous (June 2008) driver. Also, no difference. By the way, I now notice that the driver's Troubleshooting tab is grayed out and will not let me set hardware acceleration. (Can't remember if that was formerly available to me or not.) The DirectX Diagnostic Tool shows that DirectDraw Acceleration, Direct 3D Acceleration, and AGP Texture Acceleration are all enabled.
I haven't tried an earlier version of DVDFab than 5.2.x.x. Was something changed in 5.2 in the way/options for displaying the Preview?