Carelessly following these instructions, I got a WPOD.
Turns out the reason was I was copying two sections where I really only needed the second.
For the not-so-faint-of-heart;
make your child folder, such as ‘twentyten-child’ (2010, old-school, I know!)
Then you need two files to get started; style.css and functions.php as follows:
style.css
/*
Theme Name: TwentyTen Child
Theme URI: http://example.com/twenty-ten-child/
Description: TwentyTen Child Theme
Author: Joe T
Author URI: http://www.omniweb.com/wordpress
Template: twentyten
Version: 1.0.0
License: GNU General Public License v2 or later
License URI: http://www.gnu.org/licenses/gpl-2.0.html
Tags: Blargh, light, dark, two-columns, right-sidebar, responsive-layout, accessibility-ready
Text Domain: twenty-ten-child
*/
and functions.php
Then add any other files you need to customize and you’re safe from the upgrade destruction monster. Just good idea to keep an eye on when the parent theme is updated, what files are updated and make concurrent changes in any customized files (scary! but do it anyway you lazy lug [to myself]) -bye