I do not know what the cause is. I have seen similar problem with two other fansub groups releases; Triads Mahoushoujo Lyrical Nahohas episodes 9 and 10 and Nanimes Fullmoon wo sagashite episodes 17-20. Every else fansubs that I have are working fine with Mpeg4-Dvd-player. I have somewhat 100+ anime series in Mpeg4 (DivX/XviD) Dvds and all of them works well, excluding these. So really files do not usually have to be converted in order to playback these in Dvd-player that supports Avi-files!
Anyway I will also ask from Nanime and Triad what XviD preferences they have been used with these files. So that it can be solved what causes this problem and it can be prevented in future. I think that this will be in the future more relevant, because Dvd-players (and Dvd-burners) will become more and more common, and they also will be more sophisticated and Mpeg4 support will be default property. Thus it would be nice if you guys also like to tell me about your encoding preferences.