I don't know if this is related to http://wordpress.org/support/topic/nest-page-ancestors-in-34-r3 but I'm having problems with a generated subpage tree generated by code based on the Codex entry.
The function itself is available at http://pastebin.com/sqW0j9WB. It's within functions.php and is called in loop-page.php. It works fine in 3.3.2 and on the parent page in 3.4-RC3 but fails on all child pages. My guess is that it's related to