Since the DivX plugin is compiled to PPC code you have to ensure Quicktime or Safari run under Rosetta - in the finder use get Info (command-I) then click "Open using Rosetta".
Update 2006:04:12 The plugin provided by the official release of DivX Player for Macintosh is a Universal binary. You can run it native. Curiosly, the DivX Converter and DivX Player are still PPC.
Download the DivX 6 for Mac Installer.pkg
Double-click the installer to install the codec. Restart, and use Quicktime Player or Safari, to watch the latest day's work on the building (around 1.5Mb). You can also see the day at a slower pace (around 170Mb) or a directory of other views.