title: NSInvalidUnarchiveOperationException: Could not instantiate class named NSLayoutConstraint
body: <p>I am very new to this.  I followed Apple's tutorial step by step for the iPhone project "HelloWorld".  I ran it in the iPhone 5.0 simulator and it crashed:</p>
  
  <blockquote>
    <p>2012-11-02 14:46:06.782 HelloWorld[9880:c07] <strong>* Terminating app due
    to uncaught
        exception 'NSInvalidUnarchiveOperationException', reason: 'Could not instantiate
        class named NSLayoutConstraint'
        *</strong> First throw call stack:
        (0x14a2052 0xea2d0a 0x144aa78 0x144a9e9 0x32f7d7 0x32f9af 0x32f6b7 0x23036d 0xd7e2c 0xd83a9 0xd85cb 0x38a73 0x38ce2 0x38ea8 0x3fd9a
    0x10be6 0x118a6 0x20743 0x211f8 0x14aa9 0x138cfa9 0x14761c5 0x13db022
    0x13d990a 0x13d8db4 0x13d8ccb 0x112a7 0x12a9b 0x1fed 0x1f15 0x1)
        terminate called throwing an exception(lldb)</p>
  </blockquote>
  
  <p>Can someone please tell me what went wrong?  I'm using Xcode 4.5.</p>