So here's an interesting buggy thing... I have a fresh install of 1.8.4 running on MAMP (not pro). Just using the default content included, when I log into the CP and then go to view the site, the template content doesn't appear. ie. the blog listing on the home page, or calendar events... not there... just the basic layout with the sidebar stuff.
If I log out of the CP everything goes back to working again like you'd expect.
Issue with MAMP maybe?