User portal configuration

Hi there I just installed UP on a Windows 2000 server, problem is that system works when you try to access the user-portal through computer name such as “http://user-portal/factory” but if you change stServerportal in factory_const.inc from servername to to IP address so it becomes accessible from out side word system returns the following error Dash Board Error (401) access denied store.vbs Any help will be highly appreciated.