Thanks again Damien,
I looked over the guides from Renethx and have decided not to pursue exotic measures just to be able to use 7MC to play Torchwood... it's my only VC1 interlaced content at the moment, and I can use PowerDVD to watch the content on the .iso. The guide suggests I need to disable media foundation and do other significant hacks which I don't feel like spending time on.
I don't do any HD audio (just plan DD and DTS over SPDIF to an older receiver). Given that, if there's a video codec you or anyone knows about that I can simply register and enable with FilterTweaker to let me watch interlaced VC1, I'll be happy to give it a whirl. For the moment the MPCVideoDec.ax is working fine for all non-interlaced VC1 that I've got.
About MB 2.1.3, I've had it go loopy on me in both x32 and x64, and I've sent the devs som log info to help investigate. I love that program and 2.1.1 has been rock solid for me (on Vista, W7RC, W7RTM). I'm anxious to know what about my Windows 7 RTM is twigging version 2.1.3 out. If you're curious about details see the media browser forum. Most people don't run into my issues but I can see I'm not the only one, so I'm sure it will eventually be sorted and all will be right with the world again.
Meanwhile I'll backdate to 2.1.1. It does everything I want it to, pretty much the way I want to do it.