I have this situation where I receieve the following error:
java.lang.VerifyError: (class: com/xyzcorp/project/Application, method: toXML signature: ()Lorg/jdom/Element;) Incompatible argument to function
What I found out is that if you have a war that uses specific jars like jdom.jar then you need to deploy that first. After you deploy all the wars, then deploy all the ear files. Though I have not researched it better, I think there there is a different class loading mechanism for ears than for wars.