Just installed Tomacat 4.0 but can't run JSP's

I just installed Tomcat 4.0. I can run servlets fine but there is something about JSP. Sometimes I can run a jsp, but other times when I execute the same JSP i get the following error: Look like it can't find javac. My java_home env setting points to java jdk1.3.1_01, which is ok. ANy thoughts.. Please help..

type Exception report

message Internal Server Error

description The server encountered an internal error (Internal Server Error) that prevented it from fulfilling this request.

exception

javax.servlet.ServletException: sun/tools/javac/Main
      at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:485)
      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:243)
      at org.apache.catalina.core.StandardPipeline.invokeNext(StandardPipeline.java:566)
      at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:472)
      at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:943)
      at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:190)
      at org.apache.catalina.core.StandardPipeline.invokeNext(StandardPipeline.java:566)
      at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:475)
      at org.apache.catalina.core.StandardPipeline.invokeNext(StandardPipeline.java:564)
      at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:472)
      at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:943)
      at org.apache.catalina.core.StandardContext.invoke(StandardContext.java:2343)
      at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:180)
      at org.apache.catalina.core.StandardPipeline.invokeNext(StandardPipeline.java:566)
      at org.apache.catalina.valves.ErrorDispatcherValve.invoke(ErrorDispatcherValve.java:170)
      at org.apache.catalina.core.StandardPipeline.invokeNext(StandardPipeline.java:564)
      at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:170)
      at org.apache.catalina.core.StandardPipeline.invokeNext(StandardPipeline.java:564)
      at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:468)
      at org.apache.catalina.core.StandardPipeline.invokeNext(StandardPipeline.java:564)
      at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:472)
      at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:943)
      at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:174)
      at org.apache.catalina.core.StandardPipeline.invokeNext(StandardPipeline.java:566)
      at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:472)
      at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:943)
      at org.apache.catalina.connector.http.HttpProcessor.process(HttpProcessor.java:1012)
      at org.apache.catalina.connector.http.HttpProcessor.run(HttpProcessor.java:1107)
      at java.lang.Thread.run(Thread.java:484)


root cause

java.lang.NoClassDefFoundError: sun/tools/javac/Main
      at org.apache.jasper.compiler.SunJavaCompiler.compile(SunJavaCompiler.java:136)
      at org.apache.jasper.compiler.Compiler.compile(Compiler.java:272)
      at org.apache.jasper.servlet.JspServlet.loadJSP(JspServlet.java:552)
      at org.apache.jasper.servlet.JspServlet$JspServletWrapper.loadIfNecessary(JspServlet.java:177)
      at org.apache.jasper.servlet.JspServlet$JspServletWrapper.service(JspServlet.java:189)
      at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:382)
      at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:474)
      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:243)
      at org.apache.catalina.core.StandardPipeline.invokeNext(StandardPipeline.java:566)
      at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:472)
      at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:943)
      at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:190)
      at org.apache.catalina.core.StandardPipeline.invokeNext(StandardPipeline.java:566)
      at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:475)
      at org.apache.catalina.core.StandardPipeline.invokeNext(StandardPipeline.java:564)
      at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:472)
      at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:943)
      at org.apache.catalina.core.StandardContext.invoke(StandardContext.java:2343)
      at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:180)
      at org.apache.catalina.core.StandardPipeline.invokeNext(StandardPipeline.java:566)
      at org.apache.catalina.valves.ErrorDispatcherValve.invoke(ErrorDispatcherValve.java:170)
      at org.apache.catalina.core.StandardPipeline.invokeNext(StandardPipeline.java:564)
      at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:170)
      at org.apache.catalina.core.StandardPipeline.invokeNext(StandardPipeline.java:564)
      at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:468)
      at org.apache.catalina.core.StandardPipeline.invokeNext(StandardPipeline.java:564)
      at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:472)
      at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:943)
      at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:174)
      at org.apache.catalina.core.StandardPipeline.invokeNext(StandardPipeline.java:566)
      at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:472)
      at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:943)
      at org.apache.catalina.connector.http.HttpProcessor.process(HttpProcessor.java:1012)
      at org.apache.catalina.connector.http.HttpProcessor.run(HttpProcessor.java:1107)
      at java.lang.Thread.run(Thread.java:484)