Hi Tom,
This might be because the CatalogAware class uses the manage_afterAdd hook
itself (CatalogAwareness.py).
In _your_ manage_afterAdd(self, item, container), try this (untested):
def manage_afterAdd(self, item, container):
      # do whatever want to
      CatalogAware.manage_afterAdd(self, item, container)
Hope this works.
Shalabh