奇怪的session混乱问题

       服务器:jboss4.2
   问题:偶尔两个帐号在两台不同的机器上,a帐户获取了b帐号的session值
  

public actionforward loaddialoglist4inbox(actionmapping mapping,            actionform form,            httpservletrequest request,            httpservletresponse response)throws exception{        mailservice service = (mailservice)this.getbean("mailservice");        list labels = (list)request.getsession().getattribute("labels");        if(labels == null){            labels = service.loadlabelwithtotal(this.getuserid());            request.getsession().setattribute("labels",labels);        }        return mapping.findforward("dialoglist");  }