omitting www problem

I have various pages that are restricted to logged-in users. When I am logged in, if I try to navigate to “base.ext/page” instead of “www.base.ext/page” (i.e. omitting the ‘www.’ part), it redirects me to the login page even though I’m already logged in! But navigating to ‘www.base.ext/page’ works fine. Help please?

The page I need help with: [log in to see the link]