This error may have existed before updating to WordPress 3.4 because I stupidly updated both WP and WP-HTTPS at the same time. However, with WP3.4 installed, reverting back to WP HTTPS version 3.0.3 fixed the error.
Specifics: Using Tribulant's Shopping Cart plugin, shipping quote API call hangs. If SSL is deactivated the process works normally.
