in the latest version of mojoPortal you can add this in user.config then touch web.config to make it reload settings
<add key="GoogleCDNJQueryBaseUrl" value="https://ajax.googleapis.com/ajax/libs/jquery/" />
the default value is
<add key="GoogleCDNJQueryBaseUrl" value="//ajax.googleapis.com/ajax/libs/jquery/" />
which uses a protocol relative url and that normally would resolve to https if the main page is using https but with a proxy server it may not work so you need to specifically set it to use https