wp_list_pages only displaying deepest child

WordPress: 2.6.5
Plugins: Fluter, Gento, Maintenance Mode, pageMash, Role Manager, Simple Image Widget, Table of Contents Generator, WordPress Automatic Upgrade

I am attempting to list the immediate children of a page in the sidebar. So I am using:

$children = wp_list_pages('title_li=&child_of=' . $post->ID . '&depth=1&echo=0');

And it has been working wonderfully. Now bare with me as I try and give you as much info as possible. I now have a tree of pages that is 3 levels deep.

Page One
- Page One child 1
- Page One child 2
-- Page One child 2.1
-- Page One child 2.2
-- Page One child 2.3
- Page One child 3
-- Page One child 3.1
- Page One child 4
- Page One child 5

I hope this is all clear! The problem is now the wp_list_pages function above will only display “* Page One child 3.1“. If I delete “Page One child 3” (or at least make it a child of another, unrelated page) Then the wp_list_pages function Displays:

* Page One child 2.1
* Page One child 2.2
* Page One child 2.3

Each of these is incorrect as it should be displaying:

* Page One child 1
* Page One child 2
* Page One child 3
* Page One child 4
* Page One child 5

So it appears that it is displaying only the deepest child pages in the tree. Thats problem one, but what complicates this is that this structure:

Page Two
- Page Two child 1
-- Page Two child 1.1
- Page Two child 2
- Page Two child 3

Works just fine and displays the expected:

* Page Two child 1
* Page Two child 2
* Page Two child 3

If you can help me get to the bottom of this I would be very grateful, this is really bugging me!

If I can clarify anything please ask.

Thanks so much.