Indexing for sub items appears to fail after validation fail

Hi all,

I have a table with an associated (has_many) table and a single form
to edit the parent that displays the children as well.
The associated objects are represented via partials that contain
indexed fields like: <%= text_field ‘form[]’, ‘pages’ %>

When there is a validation failure in the “child” form the oddest
thing is happening, when the partial is rendered again the id is
blank and the index operator is ignored…

Does this make sense? What could be causing this?