404 Error on new blog signups; on main page as well


I've searched the forums and can't find an answer, so hopefully someone knows this issue...

I have a clean install of WPMU. The index page has the Edu Clean site on it for now. But, the links to About, for example, produce a 404 error; and blog signups send out confirmation emails but upon login, the same 404 error. The site is setup for sub-directories, not sub-domains, since Rackspace Cloud doesn't allow it. And it's a Server, not a Site.

The website is http://www.xanuu.com.

Thank you in advance for any help - aside from it driving me crazy, I am learning a lot about this...