报错：ROLLBACK TRANSACTION 请求没有对应 BEGIN TRANSACTION


        private static void Prepare(SqlConnection con, SqlCommand cmd, CommandType cmdType, string cmdText, SqlParameter[] cmdParms)
        {
            con.ConnectionString = ConnectionString;
            cmd.Connection = con;
            cmd.CommandType = cmdType;
            cmd.CommandText = cmdText;
            if (cmdParms != null)
            {
                foreach (SqlParameter parm in cmdParms)
                    cmd.Parameters.Add(parm);
            }            con.Open();
        } public static int ExecuteNonQuery(CommandType cmdType, string cmdText, params SqlParameter[] cmdParms)
        {
            using (SqlConnection con = new SqlConnection())
            {
                int iResult = -1;
                SqlCommand cmd = new SqlCommand();
                Prepare(con, cmd, cmdType, cmdText, cmdParms);
                SqlTransaction tran = con.BeginTransaction();                try
                {
                    iResult = cmd.ExecuteNonQuery();
                    tran.Commit();
                }
                catch
                {
                    tran.Rollback();
                    throw;
                }                return iResult;
            }//end using
        }
数据库是SQL Server 2000，368条Insert语句，每条语句12个字段。
之前插入都是正常的，今天突然就报错了。