jquery - Modal window close automatically

Question

i have a problem with jquery modal window. i have a modal window in which a rad grid is used. it will pop up on button click. but it doesn't work fine for me.

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

<%@ Register Assembly="Telerik.Web.UI" Namespace="Telerik.Web.UI" TagPrefix="telerik" %>
 <%@ Register Assembly="AjaxControlToolkit" Namespace="AjaxControlToolkit" TagPrefix="ajaxToolkit" %>

.auto-style1 { width: 100%; }

.modalBackground
{
    background-color: Black;
    filter: alpha(opacity=90);
    opacity: 0.8;
}
.modalPopup
{
    background-color: #FFFFFF;
    border-width: 3px;
    border-style: solid;
    border-color: black;
    padding-top: 10px;
    padding-left: 10px;
    width: 300px;
    height: 140px;
}

</style>  

<link rel="stylesheet" href="http://code.jquery.com/ui/1.10.3/themes/smoothness/jquery-ui.css" />

$(function () {

        $( "#btn_choose" )
        .button()
        .click(function() {
         $("#custmer").dialog({
          modal: true,
          buttons: {
              Ok: function () {
                  $(this).dialog("close");
              }
          }
      });
        });
         });

    <asp:ScriptManager ID="ScriptManager1" runat="server">
    </asp:ScriptManager>

    <table class="auto-style1">
        <tr>
            <td colspan="2">
                <asp:Panel ID="Panel1" runat="server" BorderColor="#000066" BorderStyle="Solid" BorderWidth="1px">
                <table class="auto-style1">
                    <tr>
                        <td style="width:15%">Customer No.</td>
                        <td style="width:10%">Customer Name</td>
                        <td style="width:10%">Current Month</td>
                        <td style="width:10%">ForecastID</td>
                        <td style="width:10%">Submitted</td>
                        <td style="width:10%">Accepted</td>

                    </tr>
                    <tr>
                        <td>
                            <asp:TextBox ID="txt_custNo" runat="server" OnTextChanged="txt_custNo_TextChanged"></asp:TextBox>
                            <asp:Button ID="btn_choose" runat="server" Text="..." BackColor="#333399" />
                        </td>
                        <td>
                            <asp:Label ID="lbl_custName" runat="server"></asp:Label>
                        </td>
                        <td>
                            <asp:Label ID="lbl_month" runat="server"></asp:Label>
                        </td>
                        <td>
                            <asp:Label ID="lbl_forecastId" runat="server"></asp:Label>
                        </td>
                        <td>&nbsp;</td>
                        <td>&nbsp;</td>

                    </tr>
                </table></asp:Panel>
            </td>
        </tr>
        <tr>
            <td>&nbsp;</td>
            <td>&nbsp;</td>
        </tr>
        <tr>
            <td>&nbsp;</td>
            <td>&nbsp;</td>
        </tr>
        <tr>
            <td colspan="2">&nbsp;</td>
        </tr>
        <tr>
            <td colspan="2">

" SelectCommand="SELECT [cmp_code] , [cmp_name] FROM [cmpny] ">

            </td>
        </tr>
    </table>

</div>
</form>