WordPress MU

I have installed and ran Mu on my website. I succesfully logged in as Admin and made some changes to the Mu dashboard, but when I went to add a new user (from the 'home page') I receive a 404 error, "This Page Cannot Be Found". So instead and went through and set up a blog through the admin panel, but when I attempt to log in under the under the user name or view the new blog, I get a 404 again. Any suggestions?

By the way, it is set up to register new blogs as sub-directories, not sub-domains

If you want to see the problem for yourself check it out at

http://www.niteroimission.com/blogs/

When you installed mu, did you include the 'www' bit within the URL? I'm wondering if that could be the issue. It shouldn't be included if you did.

I checked and I did not include the www in the URL within mu...