This seems like a bug in the plugin...
After clicking "Save", none of the plugin settings are saving. I cannot set the Port and cannot set it to Force SSL Exclusivity (or set & save any other settings).
I just updated the WordPress HTTPS plugin to version 3.0.3.
I'm running WP Multisite, WP v 3.3.2. The HTTPS plugin is not network activated. It is only activated on the main site of the multisite network.
My goal is to force HTTPS only on a few select pages on the main site, and force HTTP on all other pages.