Ok I think I found the answer but any of you more seasoned Fabrication guys can correct me if I'm wrong.
After some searching around I found this post
http://lowpitch.com/blog/puremvc-multicore-vs-standard-singlecore/ So I thought I would check to see if that method was in FabricationProxy and it was. After adding the method to my proxy all is fine.
override public function initializeNotifier(key:String):void {
super.initializeNotifier(key);
initializeProxyNameCache();
// initialize methods in proxy after this
}