In my page I have drop down control, grid view. Inside the grid view in template field I have people picker control. When ever I change the drop down value from 'Select' to another I am displaying my grid view with people picker. Everything is working fine. But after applying 'update panel', whenever I change the drop down value, people picker control is not working inside the grid view.

<asp:UpdatePanel ID="UpdatePanel1" runat="server" UpdateMode="Conditional">
      <ContentTemplate>

<asp:GridView ID="gvDirectory" runat="server" AutoGenerateColumns="false"
            ShowHeader="false" onrowcommand="gvDirectory_RowCommand"
            onrowdeleting="gvDirectory_RowDeleting"
            onrowdatabound="gvDirectory_RowDataBound" BorderWidth="0">
        <Columns>
        <asp:TemplateField>
        <ItemTemplate>
        <asp:CheckBox ID="chkselect" runat="server"  Width="20px" AutoPostBack="true"
            oncheckedchanged="chkselect_CheckedChanged"/>
        </ItemTemplate>
        </asp:TemplateField>
        <asp:TemplateField>
        <ItemTemplate>
        <asp:HyperLink ID="lnkcategory" runat="server" Text='<%# Eval("Title") %>' Target="_blank" NavigateUrl='<%# Eval("URL") %>' Width="200px" onclick="ShowAwesomeHelloPageInDialog(this);return false;"></asp:HyperLink>
        <asp:Label ID="lblvalue" runat="server" Text='<%# Eval("value") %>' Visible="false"></asp:Label>
        </ItemTemplate>
        </asp:TemplateField>
        <asp:TemplateField>
        <ItemTemplate>
          <SharePoint:PeopleEditor ID="Assignedusers" runat="server" AllowEmpty="false"
          MultiSelect="true"  Width="250px" BorderColor="#559CD7"  
          Height="20px" SelectionSet="User,SPGroup" Rows="2" PlaceButtonsUnderEntityEditor="false" EnableViewState="true" />
        </ItemTemplate>
        </asp:TemplateField>
        <asp:TemplateField HeaderText="Delete">
        <ItemTemplate>
        <asp:ImageButton ID="btnDelete" runat="server" CommandArgument='<%# Container.DataItemIndex%>' ImageUrl="~/_layouts/images/EditTaskPage/Delete.png" CommandName="Delete" Text="Delete" Height="26px" Width="26px"/>
        </ItemTemplate>
        </asp:TemplateField>
        </Columns>
        </asp:GridView>

</ContentTemplate>
      <%--<Triggers>
        <asp:PostBackTrigger ControlID="ddlCategory" />
      </Triggers>--%>      
    </asp:UpdatePanel>
    <script type="text/javascript">
      _spOriginalFormAction = document.forms[0].action;
      _spSuppressFormOnSubmitWrapper = true;
    </script>

how can I solve this problem..

thanks in advance....