updatepanel issue

hi I have the below code, whenever I click the first time or multiple time lnkCustDetails the modalpopup will show, the values(  lblCustValue.Text , custID
        lblText.Text ) will be shown blank,

But Once I click btnclose, next time onwards the values will be shown... Not sure, what is happening.. any ideas appreciated

 <asp:Button runat="server" ID="btnShowModalPopup" style="display:none"/>
     <asp:ModalPopupExtender ID="btnShowModalPopup_ModalPopupExtender"
              runat="server" DynamicServicePath="" Enabled="True"
              TargetControlID="btnShowModalPopup" PopupControlID="divPopUp"
                             CancelControlID="btnClose"
    BackgroundCssClass="popUpStyle"
    PopupDragHandleControlID="panelDragHandle"
    DropShadow="true">
          </asp:ModalPopupExtender>     
     <div class="popUpStyle" id="divPopUp" style="display:none;">
    <asp:Panel runat="Server" ID="panelDragHandle" CssClass="drag">
        Hold here to Drag this Box
    </asp:Panel>
    <asp:Label runat="server" ID="lblText" Text="CustomerID: "></asp:Label>
    <asp:Label ID="lblCustValue" runat="server"></asp:Label>
                        
    <asp:Button ID="Button1" runat="server" Text="Close" />
     
   
       

    </div>

------------------------

 
   <asp:UpdatePanel ID="pnlHelloWorld" runat="server" UpdateMode="Conditional">
    
              <ContentTemplate>
             
<asp:GridView ID="GridView1" runat="server"
                   AllowSorting="True" AutoGenerateColumns="False"  
                   Width="793px" CellPadding="0" AllowPaging="True">
                  
   
                   <Columns>
                   
                       <asp:TemplateField>
                       
                           <ItemTemplate>                       

    <div class="xcxc">Product Description:

     
                            <asp:Label ID="Label2" runat="server"  Visible="false" Text='<%# Eval("Name")%>'></asp:Label>
                  <asp:LinkButton runat="server" ID="lnkCustDetails" Text='<%# Eval("ID") %>' OnClick="lnkCustDetails_Click" />                                  
 <asp:Label ID="IsFreeShipping" runat="server"  Visible="false"></asp:Label>

   <br />
       
                      </ItemTemplate>
                       
                       </asp:TemplateField>
                      
                         
                       
                   </Columns>   
               </asp:GridView>
   
      
            </ContentTemplate>
  

    </asp:UpdatePanel>

    Protected Sub lnkCustDetails_Click(ByVal sender As Object, ByVal e As EventArgs)

        ' Fetch the customer id

        Dim lb As LinkButton = TryCast(sender, LinkButton)
        Dim custID As Integer = lb.Text
        lblCustValue.Text = custID
        lblText.Text = "are you there!!!"

   Me.btnShowModalPopup_ModalPopupExtender.Show()
        '    End Sub