Child forum problems

[Legal Chaos]

I've been trying to add some child forums for a little while now, and I can't get the results I'm looking for. Here's how it goes right now Category > Main Forum > Child Forum > (This is where I want another child forum)

Every time I add that last child forum, it just makes it a child of the main forum.

I have an image to give you to show you what I mean.

As you can see, the forum "Casual" should be a child forum of "Forge" not "Halo 3". I've looked over it a lot and I know I have the settings of the forum right.

Thanks for the help.