Getting HTML from a page behind a login

Question

This question is a follow up to my previous question about getting the HTML from an ASPX page. I decided to try using the webclient object, but the problem is that I get the

Answer 1

The only other reason I can think of then is that the web page is intentionally blocking it from loggin in. If you have access to the code, take a look at the loggin system used to see if theres anything designed to block such logins.