Is this panel brought up correctly?

Question

I'm running xcode 4.2 on Snow Leopard. I am trying to bring up a panel in a Mac application that will display alongside the main window. Here's the code for that:

- (void)applicationDidFinishLaunching:(NSNotification *)aNotification
{
    _propertiesViewController = [[NSViewController alloc] initWithNibName:@"FFPropertiesViewController" bundle:nil];
    _panelController = [[NSWindowController alloc] initWithWindowNibName:@"FFPropertiesPanel"];
    [(NSPanel*)[_panelController window] setBecomesKeyOnlyIfNeeded:YES];
    [[_panelController window] setContentView:[_propertiesViewController view]];
    [_panelController showWindow:self];

}

The panel appears to come up fine and its controls appear to be functional. But later, when I create a custom object and try to assign it to the representedObject property of the NSViewController, the assignment does not take place. Executing the following line leaves the value of representedObject as nil:

_propertiesViewController.representedObject = aFieldInfo;

I have tried giving the ViewController a property to reference the FieldInfo object, and assigning that in the same place I tried to assign representedObject. The effect is the same -- the value of the fieldInfo property remains nil after the assignment. This makes me think that there is something wrong with the ViewController. Maybe I retrieved it from the nib incorrectly?

Thanks