code is below. it works fine for edit, but errors on insert when it tries to bind the date control. text control work fine.
  

<EditFormSettings InsertCaption="Add new Comment" CaptionFormatString="Edit Comment: {0}"
                                    CaptionDataField="CultivarCommentsID" EditFormType="Template" ColumnNumber="2">
                                    <FormTemplate>
                                        <table id="Table1" cellspacing="1" cellpadding="1" border="0">
                                            <tr>
                                                <td>
                                                    Date:
                                                </td>
                                                <td>
                                                    <telerik:RadDatePicker Skin="Forest" ID="dtpCommentDate" runat="server" SelectedDate='<%# Bind( "Date" ) %>'></telerik:RadDatePicker>
                                                </td>
                                            </tr>
                                            <tr>
                                                <td>
                                                    User:
                                                </td>
                                                <td>
                                                    <telerik:RadTextBox Skin="Forest" ID="txtCommentUser" runat="server" Text='<%# Bind( "UserName") %>' Width="325" TabIndex="1">
                                                    </telerik:RadTextBox>
                                                </td>
                                            </tr>
                                            <tr>
                                                <td>
                                                    Comment:
                                                </td>
                                                <td>
                                                    <telerik:RadTextBox Skin="Forest" ID="txtComment" runat="server" Text='<%# Bind( "Comments") %>' Width="325" TabIndex="2" Rows="6" TextMode="MultiLine">
                                                    </telerik:RadTextBox>
                                                </td>
                                            </tr>
                                        </table>
                                        <table style="width: 100%">
                                            <tr>
                                                <td align="right" colspan="2">
                                                    <asp:Button ID="Button1" Text='<%# Iif (TypeOf Container is GridEditFormInsertItem, "Insert", "Update") %>'
                                                        runat="server" CommandName='<%# Iif (TypeOf Container is GridEditFormInsertItem, "PerformInsert", "Update") %>'>
                                                    </asp:Button>&nbsp;
                                                    <asp:Button ID="Button2" Text="Cancel" runat="server" CausesValidation="False" CommandName="Cancel">
                                                    </asp:Button>
                                                </td>
                                            </tr>
                                        </table>
                                    </FormTemplate>
                                </EditFormSettings>

         <telerik:RadGrid ID="grdFamily" runat="server" DataSourceID="ldsUserFamilyMembers" Skin="Vista"    Width="500px"
                 AutoGenerateColumns="false" AllowAutomaticDeletes="true" AllowAutomaticInserts="true" AllowAutomaticUpdates="true"
                    GridLines="None" PageSize="5" OnItemDataBound="RadGrid1_ItemDataBound"
                    AllowPaging="True"  >
                   
                    <MasterTableView DataKeyNames="pk_user_family_member"  TableLayout="Fixed" CommandItemDisplay="Top"  DataSourceID="ldsUserFamilyMembers" Width="500px">
                        <Columns>
                        ...
                        <telerik:GridDateTimeColumn  DataField="birth_date" PickerType="DatePicker" DataFormatString="{0:MMM dd, yyyy}" HeaderText="Birth Day" >
                            </telerik:GridDateTimeColumn>
                       ...

                        </Columns>
                        <EditFormSettings>
                            <EditColumn ButtonType="ImageButton" />
                        </EditFormSettings>
                    </MasterTableView>
                </telerik:RadGrid>

 protected void RadGrid1_ItemDataBound(object sender, GridItemEventArgs e)
        {
            if (e.Item is GridDataItem && e.Item.IsInEditMode)
            {
                GridEditableItem item = (GridEditableItem)e.Item;
                RadDatePicker datepicker = (RadDatePicker)item["DateTimeColumn"].Controls[0];
                datepicker.SharedCalendar.FastNavigationStep = 12; 
                datepicker.SharedCalendar.FastNavigationNextToolTip = "Next Month";
                datepicker.SharedCalendar.FastNavigationPrevToolTip = "Previous Month";
            }
        }

protected void RadGrid_EditCommand(object sender, GridCommandEventArgs e)

{

    GridDataItem dataItem = e.Item as GridDataItem;  

    var column = RadGrid.MasterTableView.AutoGeneratedColumns.First(i => i.HeaderText == "Name");  

    dataItem[column].Enabled = 

false;  

}