The compat auctionMonitor demo uses a preset list of colors for usernames in the chat. Each time a user joins the chat a new color is selected for them and removed from the list. The problem is the colors are not reliably added back into the list, so eventually it becomes empty. At this point a new user will be unable to join the chat as the random color chooser will throw an exception as such:

May 17, 2011 11:18:23 AM com.sun.faces.context.AjaxExceptionHandlerImpl log
SEVERE: JSF1073: javax.faces.event.AbortProcessingException caught during processing of INVOKE_APPLICATION 5 : UIComponent-ClientId=chat:join_chat_button, Message=/auctionMonitor.xhtml @260,89 actionListener="#{UserBean.enterConversation}": java.lang.IllegalArgumentException: n must be positive
May 17, 2011 11:18:23 AM com.sun.faces.context.AjaxExceptionHandlerImpl log
SEVERE: /auctionMonitor.xhtml @260,89 actionListener="#{UserBean.enterConversation}": java.lang.IllegalArgumentException: n must be positive
javax.faces.event.AbortProcessingException: /auctionMonitor.xhtml @260,89 actionListener="#{UserBean.enterConversation}": java.lang.IllegalArgumentException: n must be positive
    at javax.faces.event.MethodExpressionActionListener.processAction(MethodExpressionActionListener.java:182)
    at javax.faces.event.ActionEvent.processListener(ActionEvent.java:88)
    at javax.faces.component.UIComponentBase.broadcast(UIComponentBase.java:769)
    at javax.faces.component.UICommand.broadcast(UICommand.java:300)
    at javax.faces.component.UIViewRoot.broadcastEvents(UIViewRoot.java:794)
    at javax.faces.component.UIViewRoot.processApplication(UIViewRoot.java:1259)
    at com.sun.faces.lifecycle.InvokeApplicationPhase.execute(InvokeApplicationPhase.java:81)
    at com.sun.faces.lifecycle.Phase.doPhase(Phase.java:101)
    at com.sun.faces.lifecycle.LifecycleImpl.execute(LifecycleImpl.java:118)
    at javax.faces.webapp.FacesServlet.service(FacesServlet.java:409)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:304)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:240)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:164)
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:462)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:164)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:100)
    at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:562)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:395)
    at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:250)
    at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:188)
    at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:302)
    at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)
    at java.lang.Thread.run(Thread.java:619)
Caused by: java.lang.IllegalArgumentException: n must be positive
    at java.util.Random.nextInt(Random.java:250)
    at com.icesoft.applications.faces.auctionMonitor.ChatState.generateColorCode(ChatState.java:161)
    at com.icesoft.applications.faces.auctionMonitor.ChatState.addUserChild(ChatState.java:93)
    at com.icesoft.applications.faces.auctionMonitor.beans.UserBean.enterConversation(UserBean.java:314)
    at sun.reflect.GeneratedMethodAccessor105827.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
    at java.lang.reflect.Method.invoke(Method.java:597)
    at org.apache.el.parser.AstValue.invoke(AstValue.java:262)
    at org.apache.el.MethodExpressionImpl.invoke(MethodExpressionImpl.java:278)
    at com.sun.faces.facelets.el.TagMethodExpression.invoke(TagMethodExpression.java:105)
    at javax.faces.event.MethodExpressionActionListener.processAction(MethodExpressionActionListener.java:148)
    ... 25 more