Just to check: have you included form component in sidebar?
What do you mean with include?
My sidebar has a form and each Center JSP has an own too.
you trying to navigate a4j:include'd center content using ajax and navigation rules? It's not possible as you defining. Such navigation is possible only from included controls.
And in general - just define center content with include pointed to some EL value-binding and manage this value binding with further reRender-ing.