When trying to browse to a SharePoint web page, errors are returned:
"Error: The underlying connection was closed: An unexpected error occurred on a send"
"Server was unable to process request --> Access is denied"
The SharePoint sites open as expected when accessed from a web browser.
Windows authentication is not enabled for the site.
Open Administrative Tools | Internet Information Services [IIS] on the server that hosts the problem web site.
Enable 'Windows Authentication'
Reset IIS.
