Could be the video-file was encoded with a newer XviD codec, than the one installed on your PC and used to decode.
So I would check if a newer version is available.
(Perhaps also read second part of item 4 of my Help2Help-post
(link at bottom))
If that doesn't work please mention what is mentioned under
(rightclick >) Options > Filters > Advanced
concerning Video-playback as well as what "other player(s)" do show it.