Index: wp-admin/network/upgrade.php
===================================================================
--- wp-admin/network/upgrade.php        (revision 31466)
+++ wp-admin/network/upgrade.php        (working copy)
@@ -64,6 +64,8 @@
                        $upgrade_url = admin_url( 'upgrade.php?step=upgrade_db' );
                        restore_current_blog();
                        echo "<li>$siteurl</li>";
+                        if( strpos( $url, $your_ssl_domain ) === false )
+                                $upgrade_url = str_replace( 'https', 'http', $upgrade_url );
                        $response = wp_remote_get( $upgrade_url, array( 'timeout' => 120, 'httpversion' => '1.1' ) );
                        if ( is_wp_error( $response ) )
                                wp_die( sprintf( __( 'Warning! Problem updating %1$s. Your server may not be able to connect to sites running on it. Error message: <em>%2$s</em>' ), $siteurl, $response->get_error_message() ) );