When you delete a child page, the

{children} macro for its parent becomes unfunctional. Instead of the list of child pages, you get an error message highlighted in pink:

children: Hibernate lazy instantiation problem

Reproduction steps:
1. Create a page
2. Create a child page (i did this both by the Create Child Page link, and by creating a link first, clicking on it to make the page, and assigning the parent page by hand)
3. Remove the child page by the remove link on the page actions
4. On the parent page, add a {children}

macro.
5. The parent page will produce the above error message.

Note that this happens whether the macro is present before the child page is deleted or not. This bug propagates upwards, such that a grandparent page will show a list of its direct children, but the child with its own child missing will show the Hibernate error.