We have been working with ExProxy successfully for months with IE on XP. On Vista, the use of this proxy causes IE to fail to connect to any https site (http seems to work fine with the same proxy). I am able to get Firefox to work with the proxy on Vista just fine. When I try to access an https site in IE on Vista via the proxy and ask for a diagnosis, the response is: The configured proxy server is not responding I'm guessing this is a certificate problem of some kind (?) Thanks in advance for any insights! Scott