AnnotationMethodHandlerAdapter is loosing track of my Controllers

[portletGuy]

How does AnnotationMethodHandlerAdapter keep track of methods which are in two separate controllers?

I have two controllers: controller A (defaultHandler) and controller B. An action in controller A sets the render parameter so that controller B renders--this is successful. Here's where the breakdown occurs. An action in Controller B calls it's own action method but the action method is not found I get the error below.

org.springframework.web.portlet.NoHandlerFoundException: No matching handler method found for portlet request: 
org.springframework.web.portlet.mvc.annotation.AnnotationMethodHandlerAdapter$PortletHandlerMethodResolver.resolveHandlerMethod(AnnotationMethodHandlerAdapter.java:510)

If I take that action method from controller B and paste it to controller A, then the action method is found. Why?