Public pages blocked when logged in

Hello,

I have:
• a user group called “Members”
• a page called “Test” (which is restricted to the group “Members”)

When I’m not logged in, trying to view the page “Test” returns a 404 error, which is fine.
And when I am logged in, I can see the page “Test” but all the other public pages return a 404 error.

What did I do wrong?
Thanks

http://wordpress.org/extend/plugins/user-access-manager/