Please HELP!?! –404 Error Page Problem

Hello,

I am using WordPress version 2.7.1

I am having a problem placing pages within a Parent page on my site. I am trying to create an Author page/Biography page hierarchy on my site navigation.

When the Biography page is a “main” page on my navigation menu it appears fine –no error page 404.

BUT—when I give the Biography page a parent page (the “Author parent page) it gives me a 404 Error Page message when I click on it.

What is going on? How can I fix it?

You can see the 404 error page at this address: https://sensingarchitecture.com/author/biography/

Your help is greatly appreciated!
Mllehman