Perhaps the new .avi movie you downloaded was created with a newer codec version than the one which was installed on your PC.
How to check if the required codecs are installed on your PC you can find out under item 2 of my Help-to-Help post, a link to which is at the bottom of all my messages.
Maybe it would be a good idea to download and install newest DivX codec and see what happens starting from there. In that connection please refer to
this post (which also has link to the download-sites)