* Terminating app due to uncaught exception 'NSInvalidUnarchiveOperationException', reason: '* -[NSKeyedUnarchiver decodeObjectForKey:]: cannot decode object of class (NSLayoutConstraint)'
I have a very simple app
One view has one button
I Control Click and dragged the button to a second view and selected MODAL
When I run it in the simulator, everything works
When i run it in my iPad running iOS 5.1.1, it crashes with the error above. I have no idea why and there is no code.
This is occuring because you are using Xcode 4.5 (or previously the beta) which uses "auto layout" by default. Auto layout is only available on iOS 6 so you will get a runtime error on previous iOS versions.
You can fix this by opening your Storyboard, opening the Utilities pane, and disabling the "Use Autolayout" checkbox in the first tab/section:
For regular non-storyboard nibs, select the top-level view to access this option.
In Your Xib-> Identity and type ->Interface Builder Document -> uncheck useAutoLayout check box,this is the new feature with Ios6
来源：https://stackoverflow.com/questions/11085859/how-can-i-fix-nsinvalidunarchiveoperationexception