gridview dropdown extender

Question

hello, I have gridview with TextBox Template field and DropDownExtender so when user click on the textbox another gridview will appear that contain List of items, on row data bound for first gridview i give the data source for the second gridview. my problem is that: for few second when the page load the second gridview(in the extender ) appears in each row of the first gridview then they dissapear and work correctly any idea?
thanks

<cc1:DropDownExtender ID="uxItemExtender" runat="server" DropDownControlID="uxItemContainer" TargetControlID="uxItems">
</cc1:DropDownExtender>     
<asp:Panel BackColor="AliceBlue" ID="uxItemContainer" runat="server" ScrollBars="Both" Height="400" Width="200">       
 <asp:GridView ID="uxItemsView" runat="server" Font-Size="Small" AutoGenerateColumns="false" OnRowDataBound="uxItemsView_RowDataBound">        <Columns>        
 <asp:TemplateField HeaderText="Item Details">       
 <ItemTemplate>         
<asp:Label ID="uxItemNameLbl" Text="Name :" runat="server"></asp:Label> 
<asp:Label ID="uxItemName" runat="server"></asp:Label><br />        
<asp:Label ID="uxItemDescriptionLbl" Text="Description :" runat="server"></asp:Label>        
<asp:Label ID="uxItemDescription" runat="server"></asp:Label><br />        
<asp:Label ID="uxItemPriceLbl" Text="Price :" runat="server"></asp:Label>        
<asp:Label ID="uxItemPrice" runat="server"></asp:Label><br />        
<asp:Button ID="uxSelectItem" runat="server" Text="Add Item" OnClick="uxSelectItem_Click" /><br />        
</ItemTemplate>       
 </asp:TemplateField>        
<asp:TemplateField HeaderText="Picture">       
 <ItemTemplate>        
<asp:Image ID="uxItemImage" runat="server" Width="45" Height="50" />            </ItemTemplate>        
</asp:TemplateField>       
 </Columns>       
 </asp:GridView>       
  </asp:Panel>         
</asp:TemplateField>