Using the standard method of authentication with the HTTP proxy, port 443 is being denied. This can be seen in the packet filter log.
Under Web Security | HTTP | Advanced tab, in the MISC SETTINGS section, HTTPS is listed as one of the proxied TARGET SERVICES.
This doesn't happen all the time. For instance, many sites that have SSL protected areas work correctly through the browser. But applications like MSN and Metaframe, which use SSL, can't seem to make the final SSL connection. The apps launch and make proxied port 80 connections, but proxied 443 is denied.
This worked prior to the Beta versions.