I tried using an AMWorkflowView in a project, but when I ran it, I would crash with the following printed to the console:
*** Terminating app due to uncaught exception ‘NSInvalidUnarchiveOperationException’, reason: ‘*** -[NSKeyedUnarchiver decodeObjectForKey:]: cannot decode object of class (AMWorkflowView)’
It turns out I just forgot to include Automator.framework in my project!
It turns out that you also have to include Automator.framework to use any OSAScriptView objects.
I hope this helps someone who googles the error message :-).