Problem with Groovlets on Windows Tomcat

Has anyone actually gotten Groovlets to work on Tomcat on Windows Vista?

I am running Tomcat 6.0.18 on Vista with Java 6_07. I installed tomcat using both the service installer and from the zip file. In both cases, I installed a groovlet sample in the webapps directory with the three required jar files (groovy, antlr, asm) in the WEB-INF/lib directory. I keep getting the error that the class javax.servlet.http.HttpServlet cannot be found. I can run regular servlets and JSP files (written in Java). I also tried moving those libraries to the $CATALINA_HOME/lib directory and got the same error.

I have succeeded with Glassfish though.

Any ideas? Anyone have this working? How?

Thanks.