I have some markup:

 <f:view>
 <a4j:form styleClass="general_form">

 <fieldset class="general_form_fieldset">

 <legend class="general_form_legend">
 <h:outputText value="#{messages.booking_fieldset_resources}" />
 </legend>

 <s:validateAll>
 <div>
 <center>
 <rich:dataTable id="resourceAddedTable" var="eachResource" value="#{bookingResources}">
 <rich:column>
 <f:facet name="header">
 <h:outputText value="#{messages.booking_resource_column_header}" />
 </f:facet>
 <h:outputText value="#{messages[eachResource.inlLabel]}" />
 </rich:column>
 <rich:column>
 <f:facet name="header">
 <h:outputText value="#{messages.booking_action_column_header}" />
 </f:facet>
 <a4j:commandButton styleClass="general_form_button"
 action="#{bookingController.removeResource(eachResource)}"
 value="#{messages.general_button_remove}" type="submit" reRender="resourceAddedTable">
 </a4j:commandButton>
 </rich:column>
 </rich:dataTable>
 </center>
 </div>

 <div>
 <rich:messages id="resourceAdditionAttemptMessages" errorClass="error" warnClass="warn"
 infoClass="info" for="resourceAddedTable" />
 </div>

 <div>
 <br />
 </div>

 <div>
 <a4j:commandButton id="addResidentTrainer" value="#{messages.resource_resident_trainer}"
 action="#{bookingController.addResource('resource_resident_trainer')}"
 reRender="resourceAddedTable, resourceAdditionAttemptMessages" />

The table is simple updated by the back end when you click add.

When you click remove its supposed to remove the item from the list.

However.. I get

Caused by: java.util.ConcurrentModificationException
 at java.util.AbstractList$Itr.checkForComodification(AbstractList.java:372)
 at java.util.AbstractList$Itr.next(AbstractList.java:343)

 @DataModel
 private List<ResourceKind> bookingResources;

...

 /* (non-Javadoc)
 * @see nz.co.selwynequestriancentre.action.booking.BookingController#addResource(java.lang.String)

 */
 public String addResource(String resource) {
 log.info(">addResource " + resource);
 ResourceKind resourceKind = resourceHelper.getResourceKind(resource);
 boolean isAlreadyAdded = false;
 for (ResourceKind eachExistingResourceKind : bookingResources) {
 if (resourceKind.getInlLabel().equalsIgnoreCase(eachExistingResourceKind.getInlLabel())) {
 facesMessages.addToControlFromResourceBundle("resourceAdditionAttemptMessages", FacesMessage.SEVERITY_ERROR, "booking_resource_already_added");
 isAlreadyAdded = true;
 }
 }
 if (!isAlreadyAdded) {
 bookingResources.add(resourceKind);
 }
 log.info("<addResource");
 return null;
 }

 /* (non-Javadoc)
 * @see nz.co.selwynequestriancentre.action.booking.BookingController#removeResource(nz.co.selwyneq
uestriancentre.model.entity.Resource.ResourceKind)
 */
 public String removeResource(ResourceKind resourceKind) {
 for (ResourceKind eachExistingResourceKind : bookingResources) {
 if (resourceKind.getInlLabel().equalsIgnoreCase(eachExistingResourceKind.getInlLabel())) {
 bookingResources.remove(resourceKind);
 }
 }
 return null;
 }
...

Any ideas?