tomcat6 启动时出现异常，请高手指点迷津

最近遇到头疼的问题，希望有经验的能够帮个忙，谢谢了先。
我用的是tomcat6，启动时就报下面的错误。
信息: validateJarFile(F:\apache-tomcat-6.0.18\webapps\RiseNet\WEB-INF\lib\servlet.jar) - jar not loaded. See Servlet Spec 2.3, section 9.7.2. Offending class: javax/servlet/Servlet.class
log4j:WARN No appenders could be found for logger (org.apache.struts.util.PropertyMessageResources).
log4j:WARN Please initialize the log4j system properly.
2009-5-16 10:41:49 org.apache.catalina.core.ApplicationContext log
严重: StandardWrapper.Throwable
java.lang.NullPointerException
at org.apache.commons.digester.Digester.getXMLReader(Digester.java:899)
at org.apache.commons.digester.Digester.parse(Digester.java:1647)
at org.apache.struts.action.ActionServlet.parseModuleConfigFile(ActionServlet.java:1004)
at org.apache.struts.action.ActionServlet.initModuleConfig(ActionServlet.java:953)
at org.apache.struts.action.ActionServlet.init(ActionServlet.java:469)
at javax.servlet.GenericServlet.init(GenericServlet.java:212)
at org.apache.catalina.core.StandardWrapper.loadServlet(StandardWrapper.java:1172)
at org.apache.catalina.core.StandardWrapper.load(StandardWrapper.java:992)
at org.apache.catalina.core.StandardContext.loadOnStartup(StandardContext.java:4058)
at org.apache.catalina.core.StandardContext.start(StandardContext.java:4371)
at org.apache.catalina.core.ContainerBase.addChildInternal(ContainerBase.java:791)
at org.apache.catalina.core.ContainerBase.addChild(ContainerBase.java:771)
at org.apache.catalina.core.StandardHost.addChild(StandardHost.java:525)
at org.apache.catalina.startup.HostConfig.deployDirectory(HostConfig.java:926)
at org.apache.catalina.startup.HostConfig.deployDirectories(HostConfig.java:889)
at org.apache.catalina.startup.HostConfig.deployApps(HostConfig.java:492)
at org.apache.catalina.startup.HostConfig.start(HostConfig.java:1149)
at org.apache.catalina.startup.HostConfig.lifecycleEvent(HostConfig.java:311)
at org.apache.catalina.util.LifecycleSupport.fireLifecycleEvent(LifecycleSupport.java:117)
at org.apache.catalina.core.ContainerBase.start(ContainerBase.java:1053)
at org.apache.catalina.core.StandardHost.start(StandardHost.java:719)
at org.apache.catalina.core.ContainerBase.start(ContainerBase.java:1045)
at org.apache.catalina.core.StandardEngine.start(StandardEngine.java:443)
at org.apache.catalina.core.StandardService.start(StandardService.java:516)
at org.apache.catalina.core.StandardServer.start(StandardServer.java:710)
at org.apache.catalina.startup.Catalina.start(Catalina.java:578)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:585)
at org.apache.catalina.startup.Bootstrap.start(Bootstrap.java:288)
at org.apache.catalina.startup.Bootstrap.main(Bootstrap.java:413)
2009-5-16 10:41:49 org.apache.catalina.core.StandardContext loadOnStartup
严重: Servlet /RiseNet threw load() exception
java.lang.NullPointerException
at org.apache.commons.digester.Digester.getXMLReader(Digester.java:899)
at org.apache.commons.digester.Digester.parse(Digester.java:1647)
at org.apache.struts.action.ActionServlet.parseModuleConfigFile(ActionServlet.java:1004)
at org.apache.struts.action.ActionServlet.initModuleConfig(ActionServlet.java:953)
at org.apache.struts.action.ActionServlet.init(ActionServlet.java:469)
at javax.servlet.GenericServlet.init(GenericServlet.java:212)
at org.apache.catalina.core.StandardWrapper.loadServlet(StandardWrapper.java:1172)
at org.apache.catalina.core.StandardWrapper.load(StandardWrapper.java:992)
at org.apache.catalina.core.StandardContext.loadOnStartup(StandardContext.java:4058)
at org.apache.catalina.core.StandardContext.start(StandardContext.java:4371)
at org.apache.catalina.core.ContainerBase.addChildInternal(ContainerBase.java:791)
at org.apache.catalina.core.ContainerBase.addChild(ContainerBase.java:771)
at org.apache.catalina.core.StandardHost.addChild(StandardHost.java:525)
at org.apache.catalina.startup.HostConfig.deployDirectory(HostConfig.java:926)
at org.apache.catalina.startup.HostConfig.deployDirectories(HostConfig.java:889)
at org.apache.catalina.startup.HostConfig.deployApps(HostConfig.java:492)
at org.apache.catalina.startup.HostConfig.start(HostConfig.java:1149)
at org.apache.catalina.startup.HostConfig.lifecycleEvent(HostConfig.java:311)
at org.apache.catalina.util.LifecycleSupport.fireLifecycleEvent(LifecycleSupport.java:117)
at org.apache.catalina.core.ContainerBase.start(ContainerBase.java:1053)
at org.apache.catalina.core.StandardHost.start(StandardHost.java:719)
at org.apache.catalina.core.ContainerBase.start(ContainerBase.java:1045)
at org.apache.catalina.core.StandardEngine.start(StandardEngine.java:443)
at org.apache.catalina.core.StandardService.start(StandardService.java:516)
at org.apache.catalina.core.StandardServer.start(StandardServer.java:710)
at org.apache.catalina.startup.Catalina.start(Catalina.java:578)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:585)
at org.apache.catalina.startup.Bootstrap.start(Bootstrap.java:288)
at org.apache.catalina.startup.Bootstrap.main(Bootstrap.java:413)