I'm certain there is an easy solution. What I did was import a few avi
files into the project window. The next step I dragged the first avi
clip into the monitor window. This needed no clipping, trimming so I
dragged it into the timeline. What happens is that I can play the
audio, however, I can't see any video. It's as though it isn't there.

I opened the avi file in Media PLayer. It played out fine, audio/video.
I looked at the properties of the avi file, and indicates it to be avi.

A short background. I have a collection of DVD lecture documentaries. I
simply rip VOB to AVI and edited out redundant scenes. I've repeated
the workflow with this lecture. In this instance the video is
unavailable.

Is there a correction, adjustment, that will deliver a viewable video
of this film clip within the timeline?

Thanks