Upgrade from 1.2 to latest 1.3.3 errors

Hi
I am getting the following error after I went through the upgrade process from 1.2 to todays version of Xamarin Forms. Anybody know how to remedy his?
TIA Mark

'MonoTouch.UIKit.UIApplicationDelegate' is defined in an assembly that is not referenced. You must add a reference to assembly 'monotouch, Version=0.0.0.0, Culture=neutral, PublicKeyToken=84e04ff9cfb79065'.