present/dismissModalViewController causes UINavigationBar "Back" to lose animation
===

I have a UITableViewController that pushes a UIViewController using a UINaviationController:

    [self.navigationController pushViewController:detailViewController];

In the detailViewController, I present a modal view (a MFMessageComposeViewController for sending an SMS message) and then dismiss it, like this:

    [self presentModalViewController:smsViewController animated:YES];
    ...
    // user pushes Send or Cancel button on the view
    ...
    [self dismissModalViewControllerAnimated:YES];

The SMS modal view dismisses properly, but now when I click the "Back" button on the UINavigationBar, the views don't animate back to the table view.  The detail view just disappears and the UITableViewController's view is there.  The Back button animates and fades and the selected table cell still has the fading blue effect, but there's no view animation.

Does anyone know why the views don't animate properly?  If I don't open the SMS modal view, then the animation works properly, so I'm pretty sure it's caused somehow by the modal behavior.