I think it has to do with security issues on the Quicktime stuff…
Here’s one statement from Steinberg on the matter:
Many applications out there (not just Steinberg stuff) have been forced to put together some other option, or their users are at high security risk.
I’m not aware of the full story, but I gather Apple backed a lot of folks in the software business into a corner…they’ve decided to pull support for Quicktime on the Windows platform.
If waiting for the new engine to be optimized and features added isn’t an option, one can run the video in a plugin like VidPlayVST until the new engine is up to the task.
Muxing and Demuxing [extracting/packing a/v streams into a video format container without transcoding] isn’t a big deal these days with free utilities like ffmpeg. It’s a command line utility, but there are numerous Graphical based shells out there for folks who hate the good ole command line. Xmedia Recode is one example of a free package that includes ffmpeg and a GUI for it.
Sorry, I do realize work-arounds are not a proper fix, but that’s where we stand for now.