The installation of Domino Web Access 8 Control has been blocked or declined by the user

I’ve posted this before but thought I might try again. Does anyone know what security setting in IE7 or IE8 will allow DWA to install? Adding the site to the Trusted Sites Zone used to work in earlier versions of IE, but no longer. Looks like MS tightened the standard security setting. If I could find out which security parameter needs to be adjusted?

I know there’s a server side setting to eliminate the message (though the DWA Control still won’t install) but I don’t have access to update the server.