I installed XWiki on Linux, Tomcat, JDK 6, MySQL and everything worked. I changed the properties to validate user for view and edit and now no one can login. xwiki.log shows exeptions: apache.tomcat.util.threads.ThreadPool$ControlRunnable.run(ThreadPool.java:684) at java.lang.Thread.run(Thread.java:619) Wrapped Exception: java.lang.IllegalStateException at org.apache.catalina.connector.ResponseFacade.sendRedirect(ResponseFacade.java:432) at org.securityfilter.authenticator.FormAuthenticator.showLogin(FormAuthenticator.java:230) at com.xpn.xwiki.user.impl.xwiki.MyFormAuthenticator.showLogin(MyFormAuthenticator.java:55) at com.xpn.xwiki.user.impl.xwiki.XWikiAuthServiceImpl.showLogin(XWikiAuthServiceImpl.java:197) at com.xpn.xwiki.user.impl.xwiki.XWikiRightServiceImpl.checkAccess(XWikiRightServiceImpl.java:154) at com.xpn.xwiki.XWiki.checkAccess(XWiki.java:2548) at com.xpn.xwiki.XWiki.prepareDocuments(XWiki.java:3233) at com.xpn.xwiki.web.XWikiAction.execute(XWikiAction.java:128) at org.apache.struts.action.RequestProcessor.processActionPerform(RequestProcessor.java:431) at org.apache.struts.action.RequestProcessor.process(RequestProcessor.java:236) at org.apache.struts.action.ActionServlet.process(ActionServlet.java:1196) at org.apache.struts.action.ActionServlet.doPost(ActionServlet.java:432) at javax.servlet.http.HttpServlet.service(HttpServlet.java:709) at javax.servlet.http.HttpServlet.service(HttpServlet.java:802) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:252) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:173) at com.xpn.xwiki.web.SetCharacterEncodingFilter.doFilter(SetCharacterEncodingFilter.java:121) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:202) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:173) at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:213) at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:178) at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:126) at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:105) at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:107) at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:148) at org.apache.jk.server.JkCoyoteHandler.invoke(JkCoyoteHandler.java:199) at org.apache.jk.common.HandlerRequest.invoke(HandlerRequest.java:282) at org.apache.jk.common.ChannelSocket.invoke(ChannelSocket.java:767) at org.apache.jk.common.ChannelSocket.processConnection(ChannelSocket.java:697) at org.apache.jk.common.ChannelSocket$SocketConnection.runIt(ChannelSocket.java:889) at org.apache.tomcat.util.threads.ThreadPool$ControlRunnable.run(ThreadPool.java:684) at java.lang.Thread.run(Thread.java:619) 20:48:22,716 WARN TP-Processor3 http://www.3b-workshop.com/xwiki/bin/loginsubmit/XWiki/XWikiLogin MonitorData:log:183 - MONITOR : 1609ms 20:48:23,033 WARN TP-Processor3 http://www.3b-workshop.com/xwiki/bin/view/Main/WebHome MonitorData:log:183 - MONITOR : 292ms 20:48:23,469 WARN TP-Processor3 http://www.3b-workshop.com/xwiki/bin/login/XWiki/XWikiLogin MonitorData:log:183 - MONITOR XWiki.XWikiLogin: 424ms I have searched but can not find any mention of this issue.