Thanks for trying it !! ...i still can't figure out what's wrong.  The
left side holds a menu with 3 items.  2 of them point to almost empty
user controls (with just a text heading), the other points to a user
control with a heading, a button and a textbox... the onclick of the
button has code to simply put the current date in the textbox.  If I
click on that menu item first, it switches to that page and I can
click the button and it posts right away and displays the time... but
if i switch to another menu item and then come back to the one with
the textbox, it takes 2 clicks to get it to post correctly (when
debugging i can see it goes to the main form's Page_Onload and then to
the User Control's Page_Onload, but does not proceed to the
Button1_Click of the user control).   Here's the code, maybe someone
sees the problem?

Main form table:
----------------------------

<asp:ScriptManager ID="ScriptManager1" runat="server">
   </asp:ScriptManager>
   <asp:Table ID="Table1" runat="server" Width="100%">
       <asp:TableRow ID="TableRow1" runat="server">
           <asp:TableCell ID="TableCell1" runat="server"
ColumnSpan="2"><center>
               <asp:Label ID="Label1" runat="server" Text="Label"
CssClass="PageHeader">SIMS Admin Console</asp:Label></center></
asp:TableCell>
       </asp:TableRow>
       <asp:TableRow ID="TableRow2" runat="server">
           <asp:TableCell ID="TableCell2" runat="server" Width="20%">

                   <asp:UpdatePanel ID="UpdatePanel1" runat="server">

                   <ContentTemplate>
                       <asp:Menu ID="Menu1" runat="server"
OnMenuItemClick="Menu1_MenuItemClick" >
                           <Items>

                                   <asp:MenuItem Text="Load
Control1"></asp:MenuItem>
                                   <asp:MenuItem Text="Load
Control2"></asp:MenuItem>
                                   <asp:MenuItem Text="Load
Control3"></asp:MenuItem>

                           </Items>
                       </asp:Menu>

                   </ContentTemplate>
                   </asp:UpdatePanel>

           </asp:TableCell>

           <asp:TableCell ID="TableCell3" runat="server">
               <asp:UpdatePanel ID="UpdatePanel2" runat="server">
                   <ContentTemplate>

                   </ContentTemplate>
               </asp:UpdatePanel>
           </asp:TableCell>
       </asp:TableRow>
   </asp:Table>

Main Form Code:
------------------------------

       private const string BASE_PATH = "~/";

       protected void Page_Load(object sender, EventArgs e)
       {
           LoadUserControl();

       }

       protected void Menu1_MenuItemClick(object sender,
MenuEventArgs e)
       {
           MenuItem menu = e.Item;

           string controlPath = string.Empty;

           switch (menu.Text)
           {
               case "Load Control2":
                   controlPath = BASE_PATH +
"WebUIClientSummary.ascx";
                   break;
               case "Load Control3":
                   controlPath = BASE_PATH +
"WebUIConfigSummary.ascx";
                   break;
               default:
                   controlPath = BASE_PATH + "WebUIMainSummary.ascx";
                   break;
           }

           LastLoadedControl = controlPath;
           LoadUserControl();
       }

       private string LastLoadedControl
       {
           get
           {
               return ViewState["LastLoaded"] as string;
           }
           set
           {
               ViewState["LastLoaded"] = value;
           }

       }

       private void LoadUserControl()
       {
           string controlPath = LastLoadedControl;

           if (!string.IsNullOrEmpty(controlPath))
           {

UpdatePanel2.ContentTemplateContainer.Controls.Clear();
               UserControl uc =
(UserControl)LoadControl(controlPath);

UpdatePanel2.ContentTemplateContainer.Controls.Add(uc);
           }
       }

User Control Source:
---------------------------------

<%@ Control Language="C#" AutoEventWireup="true"
CodeBehind="WebUIClientSummary.ascx.cs"
Inherits="WebApplication1.WebUIClientSummary" %>
<p>
   Client Summary</p>
<asp:Button ID="Button1" runat="server" Text="Button"
onclick="Button1_Click" />
<asp:TextBox ID="TextBox1" runat="server"></asp:TextBox>

User Control Code:
-------------------------------

namespace WebApplication1
{
   public partial class WebUIClientSummary :
System.Web.UI.UserControl
   {
       protected void Page_Load(object sender, EventArgs e)
       {

       }

       protected void Button1_Click(object sender, EventArgs e)
       {
           TextBox1.Text = DateTime.Now.ToString();
       }
   }
}