InvalidItemStateException when adding a picture during editing of a document

• start new document
• add title, text, etc
• click on images
• upload images (toplink)
• go back to editing
• add image as link to doucment
• save

13.01.2009 09:44:27 WARN [org.apache.wicket.Localizer.getString():192] Tried to retrieve a localized string for a component that has not yet been added to the page. This can sometimes lead to an invalid or no localized resource returned. Make sure you are not calling Component#getString() inside your Component's constructor. Offending component: [MarkupContainer [Component id = panel]]
13.01.2009 09:44:40 ERROR [org.hippoecm.frontend.plugin.workflow.AbstractWorkflowPlugin.execute():231] Invalid data to save
javax.jcr.InvalidItemStateException: a0d19b47-11f8-4c19-8ef3-5d6bac1359e7: the item cannot be saved because it has been modified externally.
at org.apache.jackrabbit.core.ItemImpl.getTransientStates(ItemImpl.java:333)
at org.apache.jackrabbit.core.ItemImpl.save(ItemImpl.java:1080)
at org.hippoecm.repository.decorating.ItemDecorator.save(ItemDecorator.java:144)
at org.hippoecm.repository.impl.NodeDecorator.save(NodeDecorator.java:68)
at org.hippoecm.repository.decorating.checked.ItemDecorator.save(ItemDecorator.java:173)
at org.hippoecm.frontend.plugin.workflow.WorkflowAction.prepareSession(WorkflowAction.java:46)
at org.hippoecm.frontend.plugin.workflow.AbstractWorkflowPlugin.execute(AbstractWorkflowPlugin.java:208)
at org.hippoecm.frontend.plugin.workflow.AbstractWorkflowPlugin.access$000(AbstractWorkflowPlugin.java:52)
at org.hippoecm.frontend.plugin.workflow.AbstractWorkflowPlugin$2.onClick(AbstractWorkflowPlugin.java:143)
at org.apache.wicket.ajax.markup.html.AjaxLink$1.onEvent(AjaxLink.java:65)
at org.apache.wicket.ajax.AjaxEventBehavior.respond(AjaxEventBehavior.java:163)
at org.apache.wicket.ajax.AbstractDefaultAjaxBehavior.onRequest(AbstractDefaultAjaxBehavior.java:297)
at org.apache.wicket.request.target.component.listener.BehaviorRequestTarget.processEvents(BehaviorRequestTarget.java:100)
at org.apache.wicket.request.AbstractRequestCycleProcessor.processEvents(AbstractRequestCycleProcessor.java:91)
at org.apache.wicket.RequestCycle.processEventsAndRespond(RequestCycle.java:1175)
at org.apache.wicket.RequestCycle.step(RequestCycle.java:1252)
at org.apache.wicket.RequestCycle.steps(RequestCycle.java:1353)
at org.apache.wicket.RequestCycle.request(RequestCycle.java:493)
at org.apache.wicket.protocol.http.WicketFilter.doGet(WicketFilter.java:355)
at org.apache.wicket.protocol.http.WicketFilter.doFilter(WicketFilter.java:200)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:215)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:188)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:213)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:172)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:117)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:108)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:174)
at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:875)