Page not found appears at almost every link

I installed a fresh copy of the latest wordpress. Then I installed I themes security pro. Then I installed the Blackfyre theme. I installed the default content and bbPress. Now everywhere I click there is a page not found error. For instance if I click on the “sign up” button I get…
http://www.oursitesname.com/user-registration/
Page Not Found

The page you are looking for might have been removed, had its name changed, or is temporarily unavailable. Please try the following:

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Click the Back button in your browser to try another link.
Use a search engine like Google to look for information on the Internet.