[xwiki-devs] xwiki home page throws NullPointerException

Hi,I installed xwiki-enterprise-web-6.4.2.war on tomcat 7. I followed the installation instruction mentioned http://platform.xwiki.org/xwiki/bin/view/AdminGuide/InstallationTomcat. But I got following error on main page (http://localhost:8080/xwiki/bin/view/Main/) org.apache.catalina.core.StandardWrapperValve invokeSEVERE: Servlet.service() for servlet [action] in context with path [/xwiki] threw exceptionjava.lang.NullPointerException at com.xpn.xwiki.web.Utils.getContextComponentManager(Utils.java:699) at com.xpn.xwiki.web.Utils.getComponent(Utils.java:756) at com.xpn.xwiki.web.Utils.getComponent(Utils.java:723) at com.xpn.xwiki.web.XWikiRequestProcessor.processPath(XWikiRequestProcessor.java:47) at org.apache.struts.action.RequestProcessor.process(RequestProcessor.java:154) at org.apache.struts.action.ActionServlet.process(ActionServlet.java:1913) at org.apache.struts.action.ActionServlet.doGet(ActionServlet.java:449) at javax.servlet.http.HttpServlet.service(HttpServlet.java:620) at javax.servlet.http.HttpServlet.service(HttpServlet.java:727) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:303) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208) at com.xpn.xwiki.web.ActionFilter.doFilter(ActionFilter.java:115) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208) at org.xwiki.wysiwyg.server.filter.ConversionFilter.doFilter(ConversionFilter.java:127) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterCh at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterCh at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java at org.xwiki.container.servlet.filters.internal.SetHTTPHeaderFilter.doFilter(SetHTTPHea at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterCh at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java at com.xpn.xwiki.plugin.webdav.XWikiDavFilter.doFilter(XWikiDavFilter.java:66) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterCh at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java at org.xwiki.container.servlet.filters.internal.SavedRequestRestorerFilter.doFilter(Sav at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterCh at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java at org.xwiki.container.servlet.filters.internal.SetCharacterEncodingFilter.doFilter(Set at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterCh at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:220) at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:122) at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:50 at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:170) at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:103) at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:950) at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:116) at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:421) at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.jav at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtoco at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:316) at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1157) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:627) at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) at java.lang.Thread.run(Thread.java:863) Please help me.Thanks,Glen