Why does my ASP Server return this message
<p>I have a form which I load within a modal window in that from I have used a updatepanel and a textbox named txtAccountInfo. I have set textchange event on that textbox first time change text event fired but in the second time  textchange  shows this message.</p>

<blockquote>
  <p>uncaught exception: [Exception... "'Sys.InvalidOperationException: Sys.InvalidOperationException: Could not find UpdatePanel with ID 'uppMain'. If it is being updated dynamically then it must be inside another UpdatePanel.' when calling method: [nsIDOMEventListener::handleEvent]" nsresult: "0x8057001c (NS_ERROR_XPC_JS_THREW_JS_OBJECT)" location: "JS frame :: chrome://firebug/content/spy.js :: callPageHandler :: line 744" data: no]</p>
</blockquote>

<h2>my ASP.Net Code</h2>

<pre><code>&lt;%@ Page Language="C#" AutoEventWireup="true" CodeBehind="mAddOrder.aspx.cs"  Inherits="iSBBranch.ModalWindow.mAddOrder" %&gt;

&lt;!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"&gt;
&lt;html xmlns="http://www.w3.org/1999/xhtml"&gt;
&lt;head runat="server"&gt;
    &lt;title&gt;&lt;/title&gt;
    &lt;style type="text/css"&gt;

    &lt;/style&gt;

&lt;/head&gt;
&lt;body&gt;
    &lt;div style="width: 850px;"&gt;      
        &lt;form id="form1" class="form" action="ModalWindow/mAddOrder.aspx" runat="server"&gt;
        &lt;asp:ScriptManager ID="ScriptManager1" runat="server"&gt;
        &lt;/asp:ScriptManager&gt;
        &lt;asp:UpdatePanel ID="uppMain" UpdateMode="Conditional" runat="server"&gt;
            &lt;ContentTemplate&gt;
                &lt;asp:HiddenField ID="txtOrderType" Value="p"  runat="server" /&gt;
                 &lt;asp:HiddenField ID="txtOrderStatus" Value="n"  runat="server" /&gt;
                  &lt;asp:HiddenField ID="txtOrderRef"  runat="server" /&gt;
                &lt;fieldset id="AccountId" style="width: 783px; position:relative;"&gt;
                    &lt;legend&gt;Account Information&lt;/legend&gt;

                    &lt;p&gt;
                        &lt;label&gt;
                            *Account Number &lt;/label&gt;
                        &lt;span class="relative"&gt;
                            &lt;asp:TextBox ID="txtInvestorRef" CssClass="TextBox" runat="server"
                                OnTextChanged="txtInvestorRef_TextChanged"  AutoPostBack="True"&gt;&lt;/asp:TextBox&gt;
                            &lt;span class="&lt;%=iSBBranch.ModalWindow.mAddOrder.AccountStatus%&gt;"&gt;&lt;/span&gt;&lt;/span&gt;
                         &lt;div style="position:absolute; right:100px; top:10px;"&gt;
                         &lt;asp:UpdateProgress ID="pbContactAddress" runat="server" AssociatedUpdatePanelID="uppMain"
                                                DisplayAfter="100" DynamicLayout="true"&gt;
                                                &lt;ProgressTemplate&gt;
                                                Loading  
                                                    &lt;img alt="Loading..." src="images/info-loader.gif" /&gt;
                                                &lt;/ProgressTemplate&gt;
                                            &lt;/asp:UpdateProgress&gt;
                          &lt;/div&gt;
                &lt;/fieldset&gt;
                &lt;div class="columns"&gt;
                    &lt;!-- Left column --&gt;
                    &lt;div class="colx2-left"&gt;
                        &lt;fieldset&gt;
                            &lt;legend&gt;Post Order&lt;/legend&gt;
                            &lt;p class="inline-medium-label" style="text-align: right;"&gt;
                                &lt;label for="field1"&gt;
                                    Company&lt;/label&gt;
                                &lt;asp:DropDownList CssClass="Combobox" ID="ddlCompany" runat="server" OnSelectedIndexChanged="ddlCompany_SelectedIndexChanged"
                                    AutoPostBack="True"&gt;
                                &lt;/asp:DropDownList&gt;
                            &lt;/p&gt;
                            &lt;br class="clear" /&gt;
                            &lt;p class="inline-medium-label" style="text-align: right;"&gt;
                                &lt;label for="field1"&gt;
                                    Total Quantiy&lt;/label&gt;
                                &lt;asp:TextBox ID="txtTotalQuantity" runat="server" CssClass="NumberField" ReadOnly="true"&gt;0&lt;/asp:TextBox&gt;
                            &lt;/p&gt;
                            &lt;br class="clear" /&gt;
                            &lt;p class="inline-medium-label" style="text-align: right;"&gt;
                                &lt;label for="field1"&gt;
                                    Matured Balance&lt;/label&gt;
                                &lt;asp:TextBox ID="txtMaturedBalance" runat="server" CssClass="NumberField" ReadOnly="true"&gt;0&lt;/asp:TextBox&gt;
                            &lt;/p&gt;
                            &lt;br class="clear" /&gt;
                            &lt;p class="inline-medium-label" style="text-align: right;"&gt;
                                &lt;label for="field1"&gt;
                                    Share Quantity&lt;/label&gt;
                                &lt;asp:TextBox ID="txtShareQuantity" CssClass="NumberField" runat="server" Text="0"
                                    OnTextChanged="txtShareQuantity_TextChanged" AutoPostBack="True"&gt;&lt;/asp:TextBox&gt;
                            &lt;/p&gt;
                            &lt;br class="clear" /&gt;
                            &lt;p class="inline-medium-label" style="text-align: right;"&gt;
                                &lt;label for="field1"&gt;
                                    Rate&lt;/label&gt;
                                &lt;asp:TextBox ID="txtRate" CssClass="NumberField" runat="server" OnTextChanged="txtRate_TextChanged"
                                    AutoPostBack="True"&gt;0&lt;/asp:TextBox&gt;
                            &lt;/p&gt;
                            &lt;br class="clear" /&gt;
                        &lt;/fieldset&gt;
                    &lt;/div&gt;
                    &lt;!-- Right column --&gt;
                    &lt;div class="colx2-left" style="margin-left: 10px;"&gt;
                        &lt;fieldset&gt;
                            &lt;legend&gt;Company’s Current&lt;/legend&gt;
                            &lt;p class="inline-medium-label" style="text-align: right;"&gt;
                                &lt;label for="field1"&gt;
                                    Market Type&lt;/label&gt;
                                &lt;asp:TextBox ID="TextBox1" ReadOnly="true" CssClass="TextBox" runat="server"&gt;&lt;/asp:TextBox&gt;
                            &lt;/p&gt;
                            &lt;p class="inline-medium-label" style="text-align: right;"&gt;
                                &lt;label for="field1"&gt;
                                    Last Trade Price&lt;/label&gt;
                                &lt;asp:TextBox ID="TextBox2" runat="server" CssClass="NumberField" ReadOnly="true"&gt;&lt;/asp:TextBox&gt;
                            &lt;/p&gt;
                            &lt;p class="inline-medium-label" style="text-align: right;"&gt;
                                &lt;label for="field1"&gt;
                                    Market Lot&lt;/label&gt;
                                &lt;asp:TextBox ID="TextBox3" runat="server" CssClass="NumberField" ReadOnly="true"&gt;&lt;/asp:TextBox&gt;
                            &lt;/p&gt;
                            &lt;p class="inline-medium-label" style="text-align: right;"&gt;
                                &lt;label for="field1"&gt;
                                    Highest Price
                                &lt;/label&gt;
                                &lt;asp:TextBox ID="TextBox4" runat="server" CssClass="NumberField" Enabled="false"&gt;&lt;/asp:TextBox&gt;
                            &lt;/p&gt;
                            &lt;p class="inline-medium-label" style="text-align: right;"&gt;
                                &lt;label for="field1"&gt;
                                    Lowest Price&lt;/label&gt;
                                &lt;asp:TextBox ID="TextBox5" Enabled="false" CssClass="NumberField" runat="server"&gt;&lt;/asp:TextBox&gt;
                            &lt;/p&gt;
                        &lt;/fieldset&gt;
                    &lt;/div&gt;
                &lt;/div&gt;
                &lt;br class="clear" /&gt;
                &lt;div class=""&gt;
                    &lt;fieldset style="width: 783px;"&gt;
                        &lt;div style="float: right;"&gt;
                            &lt;p class="inline-medium-label" style="text-align: right;"&gt;
                                &lt;label&gt;
                                    Total Trade Amount&lt;/label&gt;
                                &lt;asp:TextBox ID="txtTotalTradeAmount" runat="server" CssClass="NumberField" ReadOnly="true"&gt;&lt;/asp:TextBox&gt;
                            &lt;/p&gt;
                        &lt;/div&gt;
                    &lt;/fieldset&gt;
                &lt;/div&gt;
                &lt;br class="clear" /&gt;
                &lt;div style="margin-top: 10px;"&gt;
                    &lt;asp:Button ID="btnSave" CssClass="big-button" runat="server" Text="Save" 
                        onclick="btnSave_Click" /&gt;
                    &lt;asp:Button ID="Button2" OnClientClick="return $.modal.current.closeModal();" CssClass="big-button"
                        runat="server" Text="Close" /&gt;
                &lt;/div&gt;
            &lt;/ContentTemplate&gt;
            &lt;Triggers&gt;

            &lt;asp:AsyncPostBackTrigger ControlID="btnSave" EventName="Click" /&gt;


           &lt;%-- &lt;asp:AsyncPostBackTrigger ControlID="txtInvestorRef" EventName="TextChanged" /&gt;--%&gt;
        &lt;/Triggers&gt;
        &lt;/asp:UpdatePanel&gt;
        &lt;/form&gt;
    &lt;/div&gt;
    &lt;script type="text/javascript"&gt;
        CenterWindow();
    &lt;/script&gt;
&lt;/body&gt;
&lt;/html&gt;
</code></pre>

<hr>

<p>If I close this from and again open the from then no error shows in any times on that session.</p>

<p>Please advise.</p>
