Observing Custom Node Types

[Hylton Peimer]

I created a custom node type and am trying to observe events on nodes of this 
type.

        workspace.getObservationManager().addEventListener(this,
                Event.NODE_ADDED|Event.NODE_REMOVED,
                "/root",
                true,
                null,
                new String[]{"gr:leaf"},
                false);

The custom type "gr:leaf" is defined as follows (copied from nt:unstructured).

    // The namespace declaration
    <gr = 'http://www.xyz.com'>

    [gr:leaf] > nt:base orderable
      - * (undefined) multiple COPY
      - * (undefined) COPY
      + * (nt:base) = gr:leaf multiple VERSION

I get no events!

When I omit the restriction on node-type, in addEventListener, I do see events.

Any help will be greatly appreciated.