Internet explorer 7
If the first request is a http site, for example https://www.novell.com/, both browsers will show the login page.
This is how IE7 works. What customer sees with IE7 is normal. Microsoft changed the way IE7 handles a 302 Move reply code when using a CONNECT request. Firefox will just issue another one to get the login page but IE7 will not, it will simply ignore it and it will show the error page.
Taking a lan trace on the pc using IE7 and Firefox will show this behavior.
This behavior is also documented here: