Well, I've found what the problem was. I actually had the XVid Component for Quicktime
(
http://www.apple.com/quicktime/resources/components.html) installed rather than the DiVX one I
mentioned earlier. Like I said, I needed this to view some AVI content on a journal's website.
Removing the component from the Quicktime folder in the Library folder solved my problem. AVIs
now work with JPEG, PNG and no compression. The component was version 1 alpha dating from 5th
October 2007, so I guess it needs tweaking.
Andrew.