Reluctantly I started a new thread so I could indicate in the thread title that I may have found the problem.
I defraged my hard drive; I uninstalled and reinstalled Creator 2010 and got the very same results I had before. However this morning, in desparation, I fired up VW to see how it would respond to previously created projects (productions) and earlier videos - guess what, it worked perfectly, well as perfectly as VW works.
Here's what I think happened. I wanted implicative titles on the video clips rather than FILE00001.AVI etc. I pulled the memory card from my camera, plugged it into my card reader, which of course behaves just like a flash drive, and I renamed them to like "Sloped rope entry discussion" right on the memory card. I figured that be less confusing than having one name on the camera memory card and another on my hard drive.
It is quite interesting that it is those very videos that won't load into VW, and confusing because Windows Media Player has no problem with them at all???? And BTW, the camera can't play the renamed videos either!
So I can't be sure about this until I re-shoot the videos, but since that's the first time I've tried that and it caused a problem, I think that's very likely gonna prove to be the problem. It's sad that I had some really nice clips and I won't be able to edit them. Even a conversion to another format didn't fix the problem.
As they say, "Live and learn". So the lesson here is, don't rename files on the camera's memory card.