Bug 94456 [Undo] - Resource Navigator not showing workspace undo actions
The Resource Navigator is not showing the workspace undo actions. Package Explorer is correctly working. Need to look at the difference in the way the action handlers are set up.
bundles/org.eclipse.ui.ide/src/org/eclipse/ui/views/navigator/MainActionGroup.java
* Handles a key pressed event by invoking the appropriate action,
     * delegating to the subgroups as necessary.
     */
    public void handleKeyPressed(KeyEvent event) {
        refactorGroup.handleKeyPressed(event);
        workspaceGroup.handleKeyPressed(event);
    }
    /**
     * Extends the superclass implementation to dispose the 
     * actions in this group and its subgroups.
     */
    public void dispose() {
        ResourcesPlugin.getWorkspace().removeResourceChangeListener(
                resourceChangeListener);
        newWizardMenu.dispose();
        collapseAllAction.dispose();
        exportAction.dispose();
        importAction.dispose();
        propertyDialogAction.dispose();
        toggleLinkingAction.dispose();
        gotoGroup.dispose();
        openGroup.dispose();
        refactorGroup.dispose();
        sortAndFilterGroup.dispose();
        workingSetGroup.dispose();
        workspaceGroup.dispose();
        super.dispose();
    }
}