The decoder Wam7 suggested didn't help. However
DefilerPak solved my problem. I can't remember their site URL, but I've uploaded the installer (and a readme) here:
http://www.student.itn.liu.se/~damfi208/defiler/
So basically, what I have now is:
XviD XviD-Dec DefilerPak
And it works. However I don't know if the Decoder helped in this case.
And I have not configured the DefilerPak in any way.