LinqDataSource与datetime一起用出现"System.Data.Linq.ChangeConflictException: Row not found or changed"

表结构:

CREATE TABLE [dbo].[Table1](
        [Id] [int] NOT NULL,
        [TimeCreated] [datetime] NOT NULL,
CONSTRAINT [PK_Table1] PRIMARY KEY CLUSTERED
(
        [Id] ASC
)WITH (IGNORE_DUP_KEY = OFF) ON [PRIMARY]
) ON [PRIMARY]

insert into table1(id, timecreated) values(1, getdate())

Aspx:

<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="Cus.aspx.cs"
Inherits="RfqMan4.Cus" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://
www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<html xmlns="http://www.w3.org/1999/xhtml" >
<head runat="server">
    <title>Untitled Page</title>
</head>
<body>
    <form id="form1" runat="server">
    <div>

        <asp:GridView ID="GridView1" runat="server"
AutoGenerateColumns="False"
            DataSourceID="LinqDataSource1" DataKeyNames="id">
            <columns>
                <asp:commandfield ShowEditButton="True"></
asp:commandfield>
                <asp:boundfield DataField="id" HeaderText="id"
ReadOnly="True"
                    SortExpression="id"></asp:boundfield>
                <asp:boundfield DataField="TimeCreated"
HeaderText="TimeCreated"
                    SortExpression="TimeCreated"></asp:boundfield>
            </columns>
        </asp:GridView>
        <asp:LinqDataSource ID="LinqDataSource1" runat="server"
            ContextTypeName="RfqMan4.Components.RfqManDataContext"
EnableDelete="True"
            EnableInsert="True" EnableUpdate="True"
TableName="Table1s">
        </asp:LinqDataSource>
    </div>
    </form>
</body>
</html>

每次试图更新时都会抛出ChangeConflictException异常.
奇怪的是如果把第二个列换成除datetime以外的类型,比如int, nvarchar等都能正常工作; 而Northwind里同样包含datetime列的Orders表也没有问题.
已经证实了这个问题与Id列是否自增,datetime列是否可为空,是否有默认值无关--无论任何情况下都会出现.
这个是bug,还是我忘了哪一步?