I can confirm that the 32-bit version also fails using EVR or EVR-CP under Vista 32. I haven't tried the older native renderers like VMR, etc, though. I suspect that some of the new timing work in the latest version bypasses the hooks that ambX is looking for. That said, I have found that ambX will work with Media Player Classic Home Cinema 1.3.1249 if you're using the madVR renderer (http://forum.doom9.org/showthread.php?p ... ost1316248
The quality of madVR is amazing, but is best termed as "experimental" at this point so it's not for the feint of heart (but so is MPC-HC for that matter). Also, due to some lame DRM on Microsoft's side, madVR won't work with VIDEO_TS structures. Doesn't matter if it's straight off the original disc or a homemade DVD on your hard drive with no protection ... The Microsoft DVD Navigator will only work with native renderers (you can convert the VIDEO_TS to an MKV using http://www.makemkv.com/
to route through Haali's as a workaround).
Bottom line, if you don't mind bleeding edge (you have an ambX, right?), give madVR a try. Otherwise, you're stuck with VLC or an older version of MPC-HC for the time being. And, with a little bit of tweaking, you can get a pretty good upscaled image out of VLC if you don't mind the software only route.