dragdroplayouts Addon

I am having a problem with dragdroplayouts addon. I am working with the 0.8.2 version, maven 2 and vaadin 6.7.9 with a virgo server(osgi).

I am trying to run any simple exemple using DDVerticalLayout but it shows me that error
java.lang.NoClassDefFoundError: com/vaadin/terminal/PaintTarget
at fi.jasoft.dragdroplayouts.DDVerticalLayout.paintContent(DDVerticalLayout.java:160)
at com.vaadin.ui.AbstractComponent.paint(AbstractComponent.java:781) ~[vaadin-6.7.9.jar:6.7.9]

at com.vaadin.ui.CustomComponent.paintContent(CustomComponent.java:133) ~[vaadin-6.7.9.jar:6.7.9]

The main application is:

public class MyVaadinApplication extends Application
{
private Window window;

@Override
public void init()
{
    window = new Window("My Vaadin Application");
    setMainWindow(window);

    DragdropVerticalLayoutDemo layout=new DragdropVerticalLayoutDemo();
 window.addComponent(layout);
}

}