IIS6 Windows Server 2003 GetRedirectUrl returns me back to login

[David Dixon]

Having a small issue using my ASP.NET 2.0 app on a new Windows Server 2003 R2
/ iis 6.

I have done some forms authentication using Active Directory, when the user
has logged in correctly I do a Redirect:
Response.Redirect(FormsAuthentication.GetRedirectUrl(txtUserName.Text,
false));

This works on the server when running in http://localhost/MyApp but when I
enter the server path http://server/MyApp every time I login it passes but
just takes me back to the login screen.

I have developed this on my Windows XP Pro SP2 machine using VS2005 and can
run it in localhost and http://devmachine/MyApp with no problems.

I am pretty sure that it's something to do with security of the ASP.net
application or the iis security so I have already tried entering
Administrator login details into the <identity impersonate="true"
userName="Adminstrator" password="******"/> but still no joy.

Any pointers would be a great help.

David