title: MonoTouch Error: "The Apple iPhone SDK not installed" after upgrade to iOS 5.1
body: <p>I've upgraded iOS 5.0.1 to 5.1 and I'm using MonoTouch 5.2.5 and MonoDevelop 2.8.6.5. When I created a sample applcation in MonoDevelop, it shows the error "The apple iphone sdk not installed".</p>
  
  <p>How do I get MonoTouch to work with iOS 5.1?</p>