连续调用webservice 同一个方法出错,该如何处理

function page_Load() {            data.GetNewsByCid("1", 6, onnews);                 //新闻快递本地新闻1-3            data.GetNewsByCid("8", 7, onnotice);            //公开公示8-9            data.GetNewsByCid("4", 7, onwork);                //组织工作4-7           // data.GetNewsByCid("10", 7, onlaw);               //政策法规,文件精神10-11           // data.GetNewsByCid("10", 7, onlaw);               //招商引资 12-14           // data.GetNewsByCid("10", 7, onlaw);               //村情动态15-16           // data.GetNewsByCid("10", 7, onlaw);               //特色产业17-20                     }

[WebMethod]    public DataSet GetNewsByCid(string cid, int amount)    {        string sql = "";        if (GetNewsAmountByCid(cid) > amount)        {            sql = "select top " + amount + " * from news where (classid = " + cid + ")";        }        else        {            sql = "select * from news where (classid = " + cid + ")";        }        DataSet ds = database.GetDs(sql);        return ds;    }