I've downloaded the update and opened it. It goes into an automatic install, skipping over "Destination Select". After it finished, I looked in the root Library/Application Support/Adobe/Plug-in/CS3/File Formats, and the only thing there is the older plug-in.
I can't seem to open the download to access a plug-in folder that I could drag in, and I don't know where the automatic installation ended up. Anyone else having problems with this setup?