MasterDetailPage causing Exception after upgrading to 1.3.3

Hey Xamarin,

Why is the MasterDetailPage causing this exception:

oundation.MonoTouchException: Objective-C exception thrown. Name: NSInvalidArgumentException Reason: -[__NSDictionaryI __setObject:forKey:]: unrecognized selector sent to instance 0x7bd55830

Here is my code:

Detail = new NavigationPage(new MainView())
{
BarBackgroundColor = App.Theme.HeaderColor,
BarTextColor = App.Theme.PrimaryTextColor /// THIS LINE OF CODE CAUSES THE EXCEPTION
};

This worked previously to the update.

I have a laundry list of items that are busted. NO one from support seems to be responding to my emails.

Would like some help here...