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.

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