Hi Tim,
When page names/urls are changed we automatically create a 301 redirect from the old url to the new one, but problems can occur if you then try to change it back because it will not create a circular redirect as that would put the web browser in a redirect loop.
You can fix it by checking the Administration > Advanced Tools > 301 Redirect Manager for any 301 redirect that you don't want, and you can also check the friendly url for the page under Administration > Advanced Tools > Url Manager
See also 301 Redirects
Hope that helps,
Joe