No, I cannot. Again it is not a FOP2 problem. Browsers do not allow to load cross domain sites or mix http and https on iframes (google for CORS). Its a browser limitation, that has to do with big security restrictions. If you want to load an https page, you must load FOP2 page via https also.
Here is a link describing your problem and why it is a bad idea to mix https and http within an iframe:

http://stackoverflow.com/questions/3144986/http-and-https-iframe

Here are some links with possible solutions/workarounds:

http://stackoverflow.com/questions/1653308/access-control-allow-origin-multiple-origin-domains