title: Error : NSInvalidUnarchiveOperationException: Could not instantiate class named NSLayoutConstraint
body: <p>Developed an application on iOS 6 sdk. I have both iphone and ipad version. I googled for the error message and advised disabled Auto Layout on properties of xib file. It works on iPhone 5.1 but not iPad 5.1. And i cannot figure out the exact issue. Please help me. Thanks</p>