There does not seem to be any problem with your CSS Menu Writer, you just need to setup your testing server correctly before you can preview the menu. We have some docs on setting up a local testing server and defining the site properly in DW. I'm not sure if the testing server setup covers the older G5 computers, it might be specific to Intel based machines:
Testing server for Mac
Defining a dynamic site
Today morning I have learn, that I can NOT preview page from DRW CS4 in browsers ... Most likely because of installation MAMP ... this is a real nightmare ...