Hey Joe,

Just reviewing this thread and I noticed you may be using the wrong slash in your code. You're using a forward slash (/) for the domain separator but a back slash (\) should be used.

Thanks,
Joe D.

The SSO works perfectly when I go to http://servername but when I browse to http://servername.domain.com it always asks for the logon. Any ideas?

Windows Authentication only works on a local network not on the internet. If servername.domain.com maps to a public internet ip address it will not work.

I would not recommend using Windows authentication for a site that has a public facing ip address on the internet, it should only be used on a local network/intranet. 

Users on your local network should connect over the local network not the public ip address. I'mnot positive but by exposing your site on the internet you "may" be giving hackers an opportunity for dictionary attacks to guess actual domain user credentials because IE will keep prompting until valid credentials are given.

http://msdn.microsoft.com/en-us/library/ee825205%28CS.10%29.aspx