Servlet Class cast Exception

Hi Enhydra. I need some help implementing a module into Enhydra.
I have an existing Enhydra application (mainapp) that includes the ACTION
of a form set to DoSomething.po.

I have some Servlet source code that is NOT part of an Enhydra presentation
(implements HttpPresentation) object. e.g.

public class Test extends HttpServlet
{
        public void doPost(HttpServletRequest req, HttpServletResponse res)
                           throws ServletException, IOException {

                .....
                .....
                .....
        }
}

It complies fine as part of my make.

I need to be able to call this class in an ACTION from a form.  If I
include a line in the source - 
package mainapp.presentation;
and set the ACTION to "Test.po" in the HTML page, I get a
java.lang.ClassCastException error message.

Any help would be GREATLY appreciated.

thanks