Right, so I spent a couple hours downloading this divx file, and then I get the same error you got. What the deal was is this: It was incomplete. You can fix that with a copy of DIVFIX. I think you can get a copy at www.divx-digest.com
THis guy made it with Borland Delphi:
Sarberek 603. II/6.
It will repair the index of broken files, and then when you go to resume download after watching it, you can re-strip the index so the resume works ok. I give this program a big ass thumbs up.