Need help on resolving eclipse-tomcat plugin issue

[Pat You]

Hi,
I have installed the necessary components for eclipse (J2SDK1.4.1_02, Tomcat4.1.18, Eclipse2.0, tomcat plugin and patch files). I could start Tomcat by using the Tomcat icon on eclipse menu. However, after I created a servlet - test.TestServlet( under project Tom) and try this link (http://localhost:8080/Tom/servlet/test.TestServlet) to access the servlet, I got http error 500 complaining about ClassCastException. The stack track is :
java.lang.ClassCastException
at org.apache.catalina.core.StandardWrapper.loadServlet(StandardWrapper.java:902)
at org.apache.catalina.core.StandardWrapper.allocate(StandardWrapper.java:666)
at org.apache.catalina.servlets.InvokerServlet.serveRequest(InvokerServlet.java:416)
at org.apache.catalina.servlets.InvokerServlet.doGet(InvokerServlet.java:180)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:740)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:853)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:247)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:193)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:260)
at org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(StandardPipeline.java:643)
at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:480)
at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:995)
I wonder if there is something wrong in This version of Tomcat or my incorrecting setting. I am using 4.1.18. Can anyone help me on resolving this issue? Let me know if you need more information.
Thanks