Maybe an older version of XViD (or fddshow)?
Do you have DivX5.1.1. installed?
Please check (e.g. using GSpot; see 2nd item of my
Help to Help post (link at bottom)) what (compression) codec is used to create your avi (or rather which codec is required to play it).
(Note: also try direct show render at bottom of GSpot!)
Let us know what GSpot reports