Just installed 3.0 on a Windows 2008 server on Apache.
Install went fine, admin interface is up, I can see my main blog with the wonderful new default theme, and I can create new sub-directory blogs (http://mysite.mainsite.com/blog1).
But, when I go any of my sub-directory blogs, I get the Yahoo 404 handler page. I can get to the edit page for each blog in /wp-admin/, but going directory to the blog's URL gets the 404.
I appreciate any suggestions.