WP Integration - Resource URLs Force Secure URLs (SSL) renders server unresponsive

Turning on the force secure URLs radio button and clicking on the button to submit/save the change will render the server completely unresponsive via http (page loads hang indefinitely, FTP works fine) for about five minutes, at which point everything goes back to normal, and the radio button is back in the "off" setting.

This not only affects the Wordpress install (in a subdirectory) that is using CiviCRM, but also another Wordpress install (in the parent directory) that is NOT using CiviCRM.

Manually accessing pages via HTTPS works perfectly.