The chat-portlet example is throwing the following exception:

java.util.ConcurrentModificationException
at java.util.SubList.checkForComodification(AbstractList.java:752)
at java.util.SubList.size(AbstractList.java:625)
at javax.faces.model.ListDataModel.getRowCount(ListDataModel.java:131)
at com.sun.faces.facelets.component.UIRepeat.visitChildren(UIRepeat.java:709)
at com.sun.faces.facelets.component.UIRepeat.visitTree(UIRepeat.java:642)
at javax.faces.component.UIComponent.visitTree(UIComponent.java:1601)
at javax.faces.component.UIComponent.visitTree(UIComponent.java:1601)
at javax.faces.component.UIComponent.visitTree(UIComponent.java:1601)
at javax.faces.component.UIForm.visitTree(UIForm.java:344)
at javax.faces.component.UIComponent.visitTree(UIComponent.java:1601)
at javax.faces.component.UIComponent.visitTree(UIComponent.java:1601)
at org.icefaces.impl.event.RestoreResourceDependencies.processEvent(RestoreResourceDependencies.java:24)
at javax.faces.event.SystemEvent.processListener(SystemEvent.java:106)
at com.sun.faces.application.ApplicationImpl.processListeners(ApplicationImpl.java:2168)
at com.sun.faces.application.ApplicationImpl.invokeListenersFor(ApplicationImpl.java:2144)
at com.sun.faces.application.ApplicationImpl.publishEvent(ApplicationImpl.java:302)
at com.sun.faces.application.ApplicationImpl.publishEvent(ApplicationImpl.java:246)
at javax.faces.application.ApplicationWrapper.publishEvent(ApplicationWrapper.java:670)
at javax.faces.component.UIComponentBase.encodeBegin(UIComponentBase.java:812)
at javax.faces.component.UIViewRoot.encodeBegin(UIViewRoot.java:962)
at javax.faces.component.UIComponent.encodeAll(UIComponent.java:1755)
at com.sun.faces.application.view.FaceletViewHandlingStrategy.renderView(FaceletViewHandlingStrategy.java:391)
at com.sun.faces.application.view.MultiViewHandler.renderView(MultiViewHandler.java:131)
at javax.faces.application.ViewHandlerWrapper.renderView(ViewHandlerWrapper.java:288)
at com.liferay.faces.bridge.application.ViewHandlerImpl.renderView(ViewHandlerImpl.java:91)
at com.sun.faces.lifecycle.RenderResponsePhase.execute(RenderResponsePhase.java:121)
at com.sun.faces.lifecycle.Phase.doPhase(Phase.java:101)
at com.sun.faces.lifecycle.LifecycleImpl.render(LifecycleImpl.java:139)
at com.liferay.faces.bridge.BridgePhaseResourceImpl.execute(BridgePhaseResourceImpl.java:120)
at com.liferay.faces.bridge.BridgeImpl.doFacesRequest(BridgeImpl.java:96)
...