1) login to jbpm-console
2) navigate to Processes tab and start Evaluation process
3) click on Execution history and click refresh - this action fire the exception:

2011-03-02 10:46:40,470 [INFO ] Loaded 0 tasks
2011-03-02 10:46:42,739 [DEBUG] ToolID: Process_Overview.4
2011-03-02 10:46:45,238 [DEBUG] GET: http://localhost:8080/gwt-console-server/rs/process/definitions
2011-03-02 10:46:45,250 [INFO ] Loaded 1 process definitions in 2 ms
2011-03-02 10:46:49,490 [DEBUG] ToolID: Execution_History.3
2011-03-02 10:46:49,541 [DEBUG] New subscription: org.jboss.bpm.console.client.process.UpdateHistoryDefinitionAction -> org.jboss.bpm.console.client.process.UpdateHistoryDefinitionAction$1@273
2011-03-02 10:46:49,542 [DEBUG] New subscription: org.jboss.bpm.console.client.process.UpdateHistoryInstanceAction -> org.jboss.bpm.console.client.process.UpdateHistoryInstanceAction$1@274
2011-03-02 10:46:49,545 [DEBUG] New subscription: appContext.model.listener -> org.jboss.bpm.console.client.process.DefinitionHistoryListView$4@27e
2011-03-02 10:46:50,047 [DEBUG] GET: http://localhost:8080/gwt-console-server/rs/process/definitions
2011-03-02 10:46:50,062 [INFO ] Loaded 1 process definitions in 1 ms
2011-03-02 10:46:52,509 [ERROR] No subscribers for: JBPM_HISTORY_SERVICE<br/>Additional details:<br/>Attempt to send message to subject for which there are no subscribers