UINavigationBar topItem/items seems to double-pop on back

Question

I am managing my own UINavigationBar. I need to do this due to extensive skinning. The documentation for UINavigationController warns that there are limitations to skinning the UINavigationBar when used with a UINavigationController.

I have put in extensive logging and from everything I can tell, pushing the "Back" button in the UINavigationController pops two items off of of the stack instead of one. I get a single delegate callback telling me that it is removing the logical item, but it actually removes that one and one more.

The item added to the UINavigationController in awakeFromNib should never be removed. It is being removed for some reason.

There are two similar questions, but neither have satisfactory answers. The two questions are:

http://stackoverflow.com/questions/2154082/uinavigationbar-items-accessor-doesnt-return-the-current-uinavigationitem

http://stackoverflow.com/questions/1280580/uinavigationbar-seems-to-pop-2-items-off-stack-on-back

- (void)awakeFromNib {
    [headerView setDelegate: self];
    [headerView pushNavigationItem: tableDisplay animated: NO];
}

- (void) selectedStory: (NSNotification *)not {
    [headerView pushNavigationItem: base animated: NO];
    NSLog(@"Selected story: %@", base);
}

- (void) baseNav {
    NSLog(@"Current items: %@", [headerView items]);
    BaseInnerItem *current = (BaseInnerItem *)[headerView topItem];
    [self addSubview: [current view]];
}

- (BOOL)navigationBar: (UINavigationBar *)navigationBar shouldPushItem: (UINavigationItem *)item {
    return YES;
}

- (BOOL)navigationBar: (UINavigationBar *)navigationBar shouldPopItem: (UINavigationItem *)item {
    return YES;
}

- (void)navigationBar:(UINavigationBar *)navigationBar didPushItem:(UINavigationItem *)item {
    NSLog(@"didPushItem: %@", item);
    [self baseNav];
}

- (void)navigationBar:(UINavigationBar *)navigationBar didPopItem:(UINavigationItem *)item {
    NSLog(@"didPopItem: %@", item);
    [self baseNav];
}

Edited to add relevant debugging from a single run:

2010-10-13 02:12:45.911 Remix2[17037:207] didPushItem: <TableDisplay: 0x5d41cc0>
2010-10-13 02:12:45.912 Remix2[17037:207] Current items: (
    "<TableDisplay: 0x5d41cc0>"
)
2010-10-13 02:12:49.020 Remix2[17037:207] didPushItem: <WebDisplay: 0x591a590>
2010-10-13 02:12:49.021 Remix2[17037:207] Current items: (
    "<TableDisplay: 0x5d41cc0>",
    "<WebDisplay: 0x591a590>"
)
2010-10-13 02:12:49.023 Remix2[17037:207] Selected story: <WebDisplay: 0x591a590>
2010-10-13 02:12:59.498 Remix2[17037:207] didPopItem: <WebDisplay: 0x591a590>
2010-10-13 02:12:59.499 Remix2[17037:207] Current items: (
)