I don't think it is a problem with my player as both the older 1.xx versions of
DivXToDVD got it right, and Avi2DVD gets it right. I think ConvertX is not getting it right when you have a movie that is in a widescreen format, but is not fully widescreen and so has bars at the top and bottom. Instead of leaving the bars at the top, and showing the full width, ConvertX will chop the sides off and stretch what's left out to a widescreen format.
Almost looks like ConvertX is only considering the movie part of the stream, and not counting any black bars that are part of the picture, so it's getting size/aspect ratio wrong.