Just installed the same plugin for WP 3.3.1
To activate it go to: Settings > Writing > HTML Mode Locker and check the box for pages and/or posts. After you save the settings you’ll see the plugin when editing pages/posts.
It seems that this plugin wasn’t what I was looking for. I was hoping that I would get rid off the extra HTML that WP is adding to my code.
I should learn to read, the plugin name is “HTML Mode Locker” not “Stop WP from adding extra HTML to my code” ??
Back to testing…