Okay, issue resolved. Problem was in the class annotated with @XmlRootElement, @XmlElement, etc. all of the getter and setters were correct for the member variables, however I had named one method "getCopy" to create a deep copy of the POJO. Jackson, upon converting to JSON, evidently was trying to match this to a member variable "copy", couldn't find it and threw an exception.
So, for any helper methods in your RESTEasy POJO's, DO NOT begin with get or set unless they correspond to a member variable.