WP 2.5 upgrade: Page/Child address problem

I upgraded to version 2.5 yesterday and have now found that one of my pages won’t load properly.

For some reason, the child loads as the parent. Here are links to the two pages:

https://www.sitkanature.org/photojournal/
https://www.sitkanature.org/photojournal/2007/

If I change the slug for the child slug to yr2007, it works correctly. However, I would prefer not to do that, if I can avoid it, as I’ve already established this convention.