Getting error for generic interface: The interface Observer cannot be implemented more than once with different arguments:

I am getting this error in Eclipse while writing a GWT app

The interface Observer cannot be implemented more than once with different arguments: Observer and Observer

public class CompositeWordLists extends Composite implements Observer<DialogBoxAuthenticate>, Observer<CompositeListData>

Here is the interface

public interface Observer<T> {
    public void update(T o);
}

Is this right? How can I get around this problem without having to create a multitude of Observer classes for every possible event?