Weird layout problem with UINavigationController

I've configured a NIB as follows:

...but when I display this NIB as a modal view con开发者_开发百科troller, it appears on the simulator as:

I recall seeing this problem a long time ago on a project, but I can no longer remember what I did to fix it. Any idea what I've done wrong here?

Thanks very much.

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The class of your Social Settings view controller is set to UIViewController. Shouldn't that be UITableViewController or a subclass of it?