[Java-gnome-developer] error defining signals with glade

[<ga...@cw...>]

hiya,
i am trying to write a simple app using java-gnome and glade, but i
receive an error whenever i try to define a signal for a button in
glade.

the error says:
java.lang.reflect.InvocationTargetException: ListenerDelegate.create
failure

i receive this with sun's javavm 1.5 and gij-4, and i receive this for
each signal i have defined...

anyway, i am on ubuntu hoary, versions libgtk2-java/libglade-java:
2.8.3-2

Sourcecode:

public class HotplugManager {

	LibGlade glade;
	
	public HotplugManager() throws GladeXMLException, 
                                       FileNotFoundException, 
                                       IOException {
		glade = new LibGlade("data/hotplugmanager.glade", this);
	}
	
	public static void main(String[] args) {
		
		HotplugManager hotplugman;
		
		Gtk.init(args);
		try {
			hotplugman = new HotplugManager();
		} catch(Exception e) {
			e.printStackTrace();
		}
		Gtk.main();
		
	}
}

as you can see, i am not trying to catch the signal it is only defined
in the glade file: 
<widget class="GtkButton" id="button_execute">
		  <property name="visible">True</property>
		  <property name="can_default">True</property>
		  <property name="can_focus">True</property>
		  <property name="label">gtk-execute</property>
		  <property name="use_stock">True</property>
		  <property name="relief">GTK_RELIEF_NORMAL</property>
		  <property name="focus_on_click">True</property>
		  <signal name="clicked" handler="on_button_execute_clicked"
last_modification_time="Fri, 27 May 2005 20:56:57 GMT"/>
</widget>

does anyone have any ideas? 
thanks in advance
cheers
gaboro