Matt,
I used an AVI Splitter program to create a 30 second segment from the 30 minute AVI file. The file segment was not transcoded. The short segment played fine in MC18. I then created a segment from 1 minute in to the end of the file which also played fine. Lastly, I created a segment of the first eleven seconds thinking that there might be a timing error in the first few frames. This lead in segment also played correctly. Lastly I used the AVI splitter to save the entire file with no transcoding and this also played correctly. The MediaInfo for this file was identical to the original.
I played other shorter AVI files that were created by the same screen video capture program and they also played correctly.
The problem file plays correctly in Media Player Classic, VLC Media Player, Windows Media Player and Nero Showtime.
At this point I consider the AVI Splitter as a workaround if I run into another problem AVI file. Its interesting that a saved copy of the file had the same problem but the AVI Splitter program somehow corrected whatever was causing the problem for MC18.
Matt, thanks again for your support.
Derek