I have a problem with child pages.
I have suppressed all plugins and for debugging puposes I uses the simplest Theme: Twenty Twelve. But the problem is the same with all the other themes I tried.
I declare three pages Page 1, Page 2, Page 1.1. As you might have guessed Page 1.1 is Page 1's child. And I declare Page 1.1 having Page 1 for parent.
Then I create a menu and add all my pages in it.
I drag Page 1.1 under Page 1 and indent it to the right. Then I save the menu and everything works just fine.
Now I create two new pages Page 1.2 and Page 1.3 children of Page 1.
I go to menu, add the new pages, drag them under Page 1 and indent them.
But, as I save the menu, the indentation of 1.1, 1.2 and 1.3 just vanished. They are set back as orphan pages and that's how they appear in the site.
In order to try to understand what went wrong, I delete Page 1.2 and Page 1.3 to go back to the initial situation.
And there the problem is the same: indentation of 1.1 (the only child now) vanishes as I save the menu.
Could anywone help me with that? What did I do wrong?