I had exactly the same problem. I changed one line in /includes/swift-framework/options/defaults.php and everything works fine.
// $wp_content_url = ( is_ssl() ? str_replace( 'http://', 'https://', WP_CONTENT_URL ) : WP_CONTENT_URL );
$wp_content_url = ( is_ssl() ? str_replace( 'http://', 'https://', get_option('siteurl')) : get_option('siteurl'));