Ajax pop up disappears instantly while partial postback

Dear All,

I am using ajax popup extender to show the confirmation message for editing the row in gridview. But the pop up opens and disappear instantly.

Following is the code

<script type="text/javascript" language="javascript">
    function showModel() {
            $find('editConfirm').show();
        }
        function onOk() {
        return true; }</script><asp:Button ID="btnnoshow" runat="server" Style="display: none" meta:resourcekey="btnnoshowResource1" /><ajaxToolkit:ModalPopupExtender ID="modalAddLang" runat="server" PopupControlID="pnladdLang"
        BackgroundCssClass="modalBackground" TargetControlID="btnnoshow" RepositionMode="RepositionOnWindowScroll"></ajaxToolkit:ModalPopupExtender><asp:Panel ID="pnladdLang" runat="server" Style="display: none;" CssClass="modalPopup"
        meta:resourcekey="pnladdLangResource1"><asp:UpdatePanel ID="UpdatePanel11" runat="server"><ContentTemplate><table width="100%" border="0" cellpadding="0" cellspacing="10"><tr><td><asp:GridView ID="GridView2" runat="server" AutoGenerateColumns="False" DataKeyNames="DESC_ID,LCID"
                                            OnRowCommand="GridView2_RowCommand" OnRowCancelingEdit="GridView2_RowCancelingEdit"
                                            OnRowDeleting="GridView2_RowDeleting" OnRowEditing="GridView2_RowEditing" OnRowUpdating="GridView2_RowUpdating"
                                            OnRowDataBound="GridView2_RowDataBound" BorderWidth="0px" BorderStyle="None"
                                            GridLines="None" Width="100%" meta:resourcekey="GridView2Resource1"><Columns><asp:TemplateField HeaderText="Business Description" meta:resourcekey="TemplateFieldResource1"><EditItemTemplate><asp:Label ID="lblcnt2" runat="server" Text="" ForeColor="Cyan"></asp:Label>&nbsp;<asp:Label ID="lblgrddetails" runat="server" Text="Characters remaining" meta:resourcekey="Label3Resource1"></asp:Label><br /><asp:TextBox ID="edtBizdesc" runat="server" TextMode="MultiLine" Height="80px" Width="200px"
                                                            Text='<%# Bind("DESC_TXT") %>' onkeypress="return textboxMultilineMaxNumber(event, this,300);"
                                                            onKeyUp="Count2(this, 300);" onChange="Count2(this,300);" MaxLength="300" meta:resourcekey="edtBizdescResource1"></asp:TextBox><div><asp:RequiredFieldValidator runat="server" ID="rfvaldesc1" ControlToValidate="edtBizdesc"
                                                                Display="Dynamic" ErrorMessage="Business description is required" ValidationGroup="EditGroup"
                                                                CssClass="errortext" meta:resourcekey="rfvaldesc1Resource1"></asp:RequiredFieldValidator><asp:RegularExpressionValidator runat="server" ID="RgDescriptionlngedit" ValidationExpression="[\s\S]{0,300}"
                                                                ValidationGroup="EditGroup" Display="Dynamic" ErrorMessage="Maximum 300 characters allowed"
                                                                ControlToValidate="edtBizdesc" CssClass="errortext" meta:resourcekey="RgDescriptionlngeditResource1"></asp:RegularExpressionValidator></div></EditItemTemplate><ItemTemplate><asp:TextBox ID="Bizdesc" runat="server" Height="80px" ReadOnly="True" Text='<%# Eval("DESC_TXT") %>'
                                                            TextMode="MultiLine" Width="200px" meta:resourcekey="BizdescResource2"></asp:TextBox></ItemTemplate><HeaderStyle CssClass="table1header" /><ItemStyle CssClass="tableborder5" /></asp:TemplateField><asp:TemplateField HeaderText="Language" meta:resourcekey="TemplateFieldResource2"><%--<EditItemTemplate><asp:DropDownList ID="edtddlLang" runat="server" meta:resourcekey="edtddlLangResource1"></asp:DropDownList></EditItemTemplate> --%><ItemTemplate><asp:Label ID="lblLang" runat="server" Text='<%# Eval("LANG") %>' meta:resourcekey="lblLangResource1"></asp:Label><asp:HiddenField runat="server" ID="hfnLcid" Value='<%# Eval("LCID") %>' /></ItemTemplate><HeaderStyle CssClass="table1header" /><ItemStyle CssClass="tableborder5" /></asp:TemplateField><asp:TemplateField HeaderText="Edit" ShowHeader="False" meta:resourcekey="TemplateFieldResource3"><EditItemTemplate><asp:LinkButton ID="LinkButton1" runat="server" CommandName="Update" Text="Update"
                                                            ValidationGroup="EditGroup" meta:resourcekey="LinkButton1Resource1"></asp:LinkButton><asp:LinkButton ID="LinkButton2" runat="server" CausesValidation="False" CommandName="Cancel"
                                                            Text="Cancel" meta:resourcekey="LinkButton2Resource1"></asp:LinkButton></EditItemTemplate><ItemTemplate><asp:LinkButton ID="lnkEdit1" runat="server" CommandName="Edit" CausesValidation="False"
                                                            Text="Edit" OnClientClick="showModel();"  meta:resourcekey="lnkEdit1Resource1"></asp:LinkButton></ItemTemplate><HeaderStyle CssClass="table1header" /><ItemStyle CssClass="tableborder5" /></asp:TemplateField><asp:TemplateField HeaderText="Delete" ShowHeader="False" meta:resourcekey="TemplateFieldResource4"><ItemTemplate><asp:LinkButton ID="lnkDelete" runat="server" CausesValidation="False" CommandName="Delete"
                                                            Text="Delete"  OnClientClick="showDeleteModel();"  meta:resourcekey="lnkDeleteResource1"></asp:LinkButton></ItemTemplate><HeaderStyle CssClass="table1header" /><ItemStyle CssClass="tableborder5" /></asp:TemplateField></Columns></asp:GridView></td></tr><tr><td align="right" valign="middle"><asp:Button ID="btnfinish" runat="server" Text="Finish" CssClass="button" OnClick="btnfinish_Click"
                                            CausesValidation="False" meta:resourcekey="btnfinishResource1" /></td></tr></table></ContentTemplate><Triggers><asp:PostBackTrigger ControlID="btnfinish" /><asp:PostBackTrigger ControlID="LinkButton4" /><asp:PostBackTrigger ControlID="GridView2" /></Triggers></asp:UpdatePanel></asp:Panel><asp:Button ID="cmdokEdit" runat="server" Style="display: none"/><ajaxToolkit:ModalPopupExtender ID="editConfirm" runat="server" BackgroundCssClass="modalBackground"
     PopupControlID="Panel1" TargetControlID="cmdokEdit"  BehaviorID="editConfirm" OkControlID="OkButton"  CancelControlID="CancelButton" ></ajaxToolkit:ModalPopupExtender><asp:Panel ID="Panel1" runat="server" Style="display: none;" CssClass="modalPopup"><asp:UpdatePanel ID="UpdatePaneedit" runat="server"><ContentTemplate><table width="100%" border="0" cellpadding="0" cellspacing="0"><tr><td align="left" valign="middle" class="popupheader"><asp:Label ID="Label15" runat="server" Text="Business Description" meta:resourcekey="lblheadertxtResource1"></asp:Label></td>   </tr><tr><td><asp:Label ID="lbleditmessage" runat="server" Text="Do you want to edit the record?"></asp:Label></td></tr><tr><td><asp:Button ID="OkButton" runat="server" CssClass="button" Text="OK"></asp:Button><asp:Button ID="CancelButton" runat="server" CssClass="button" Text="Cancel"></asp:Button></td></tr></table></ContentTemplate></asp:UpdatePanel></asp:Panel>

Please help me.