Updated data is overwritten.

[Taiji]

I use editing Grid. Grid is like that.

Person | month | target
John | 2012/01 | 10
John | 2012/02 | 12 
John | 2012/03 | 11 
John | 2012/04 | 15 
John | 2012/05 | 15 
...

When I set  '9' on John 2012/02 and 2012/04 target,

Person | month | target
John | 2012/01 | 10
John | 2012/02 | 9 
John | 2012/03 | 11 
John | 2012/04 | 9
John | 2012/05 | 15 
...

And click save button , Grid shows like that,

Person | month | target
John | 2012/01 | 10
John | 2012/01 | 10 
John | 2012/03 | 11 
John | 2012/01 | 10 
John | 2012/05 | 15 
... 
 
Update has succeeded and the data Server responsed was correct. 
Why this situation happen?
 
Source is like that.

var grid = $("#grid2").kendoGrid({

    dataSource: {

        transport: {

            read: {

                url:"getList.asp",

                dataType: "json" ,

                data : {

                    'entity': 'goal',

                    'termStartStart' : '2011/04/01',

                    'empCd' : 'sato',

                    PG : 1

                }

            },

             update: {

                url: "update.asp",

                dataType: "json" ,

                type : 'POST',

                data : {

                    entity : 'goal',
                            's_termStartStart' : '2011/04/01',

                    's_empCd' : 'sato',

                    's_PG' : 1

                }

            }

        },

        schema : {

            data : function(data){

              

                var new_data = [];

                return new_data;

            },

            model: {

                id: "reportId",

                fields: {

                    reportId : {type : 'number', editable : false},

                    empName: { editable: false },

                    termStart: { editable: false },

                    volume: {

                        type: "number",

                        validation: {

                                    max : { value : 1000,  message : "目標訪問数は1000以内にしてください"}

                         }

                    }

                }

            }

             

        }

    },

    height: 380,

    sortable: true,

    editable: true,

        toolbar: [

            { name: "save", text: "保存する" },

            { name: "cancel", text: "キャンセル" },

            { name : "年度", template :  ' <input id="input" />' }

        ],

        columns: [ {

                field: "empName",

                width: 90,

                title: "社員"

            } , {

                field: "termStart",

                width: 40,

                title: "月"

            } , {

                field: "volume",

                width: 35,

                title: "目標訪問数",

                format: "{0:d}"

            }

        ]

});