I even don't know what is problem.
The stacktrace is like this:
ERROR - Tue Nov 20 11:15:20 CST 2012: Error when creating task on task server for work item id 176. Error reported by task server: Task operation request timed out
java.lang.RuntimeException: Task operation request timed out
at org.jbpm.task.service.SyncTaskServiceWrapper.addTask(SyncTaskServiceWrapper.java:118)
at org.jbpm.process.workitem.wsht.GenericHTWorkItemHandler.executeWorkItem(GenericHTWorkItemHandler.java:145)
at org.drools.persistence.jpa.processinstance.JPAWorkItemManager.internalExecuteWorkItem(JPAWorkItemManager.java:55)
at org.jbpm.workflow.instance.node.WorkItemNodeInstance.internalTrigger(WorkItemNodeInstance.java:105)
at org.jbpm.workflow.instance.impl.NodeInstanceImpl.trigger(NodeInstanceImpl.java:124)
at org.jbpm.workflow.instance.impl.NodeInstanceImpl.triggerNodeInstance(NodeInstanceImpl.java:205)
at org.jbpm.workflow.instance.impl.NodeInstanceImpl.triggerCompleted(NodeInstanceImpl.java:164)
at org.jbpm.workflow.instance.impl.ExtendedNodeInstanceImpl.triggerCompleted(ExtendedNodeInstanceImpl.java:47)
at org.jbpm.workflow.instance.node.StateBasedNodeInstance.triggerCompleted(StateBasedNodeInstance.java:162)
at org.jbpm.workflow.instance.node.StateBasedNodeInstance.triggerCompleted(StateBasedNodeInstance.java:143)
at org.jbpm.workflow.instance.node.WorkItemNodeInstance.triggerCompleted(WorkItemNodeInstance.java:239)
at org.jbpm.workflow.instance.node.HumanTaskNodeInstance.triggerCompleted(HumanTaskNodeInstance.java:90)
at org.jbpm.workflow.instance.node.WorkItemNodeInstance.workItemCompleted(WorkItemNodeInstance.java:301)
at org.jbpm.workflow.instance.node.WorkItemNodeInstance.signalEvent(WorkItemNodeInstance.java:277)
at org.jbpm.workflow.instance.impl.WorkflowProcessInstanceImpl.signalEvent(WorkflowProcessInstanceImpl.java:326)
at org.drools.persistence.jpa.processinstance.JPAWorkItemManager.completeWorkItem(JPAWorkItemManager.java:121)
at org.drools.command.runtime.process.CompleteWorkItemCommand.execute(CompleteWorkItemCommand.java:69)
at org.drools.command.runtime.process.CompleteWorkItemCommand.execute(CompleteWorkItemCommand.java:32)
at org.drools.command.impl.DefaultCommandService.execute(DefaultCommandService.java:36)
at org.drools.persistence.SingleSessionCommandService.execute(SingleSessionCommandService.java:367)
at org.drools.command.impl.CommandBasedStatefulKnowledgeSession$1.completeWorkItem(CommandBasedStatefulKnowledgeSession.java:150)
at org.jbpm.process.workitem.wsht.GenericHTWorkItemHandler$TaskCompletedHandler.handleCompletedTask(GenericHTWorkItemHandler.java:221)
at org.jbpm.process.workitem.wsht.GenericHTWorkItemHandler$TaskCompletedHandler$1.run(GenericHTWorkItemHandler.java:187)
at java.lang.Thread.run(Thread.java:722)