Only one instance of a RadAjaxManager can be added to the page!

What should I do?  

TIA

I have an dropdown list and a div. This div contains two usercontrols.
Based on the value selected in the dropdown i want to Display only one usercontrol in the div.
How should I achieve it. please tell what are the settings i will have to do in the RadAjaxManager and all the required things that i need to make?

For example

  <telerik:RadAjaxLoadingPanel ID="RadAjaxLoadingPanel1" runat="server" Skin="Telerik" Visible="true"
            InitialDelayTime="40" />
  <telerik:RadAjaxManagerProxy ID="RadAjaxManagerProxy1" runat="server"  >
   <AjaxSettings>
    <telerik:AjaxSetting AjaxControlID="selUserControl"  EventName="OnSelectedIndexChanged">
     <UpdatedControls>
      <telerik:AjaxUpdatedControl ControlID="divUserControlSection" LoadingPanelID="RadAjaxLoadingPanel1" />
                    </UpdatedControls>
    </telerik:AjaxSetting>
    </AjaxSettings>
  </telerik:RadAjaxManagerProxy>
 <div>
  <div>
      <telerik:RadComboBox ID="selUserControl" CausesValidation="false" runat="server"
                        AppendDataBoundItems="false"  DataTextField="Text" DataValueField="Value"
                        OnSelectedIndexChanged="selUserControl_SelectedIndexChanged" AutoPostBack="true">
    </telerik:RadComboBox>
  </div>
  <div class="label-container" id="objectTypeSection" runat="server">
   <uc:UserControl1 id="usercontrol1" runat="server">
   <uc:UserControl2 id="usercontrol2" runat="server">
  </div> 
 </div> 
   
   

void RadGrid1_InsertCommand(object sender, GridCommandEventArgs e)

{

try

//Get the GridEditFormInsertItem of the RadGrid

GridEditFormInsertItem insertedItem = (GridEditFormInsertItem)e.Item;

RadComboBox RadCombobox = insertedItem.FindControl("RadComboBoxArea") as RadComboBox;

string strArea = RadCombobox.SelectedItem.Text; //Area

 RadCombobox = insertedItem.FindControl(

"RadComboBoxFMT") as RadComboBox; 

string strFMT = RadCombobox.SelectedItem.Text; //FMT or Asset

"RadComboBoxField") as RadComboBox; 

string strField = RadCombobox.SelectedItem.Text; //Field

 RadCombobox = insertedItem.FindControl(

"RadComboBoxWell") as RadComboBox;  

string strWell = RadCombobox.SelectedItem.Text; //Well 

"RadComboBoxUnloadType") as RadComboBox;  

string strUnloadType = RadCombobox.SelectedItem.Text; //Unload Type  

RadDatePicker EventStartDateTime = (RadDatePicker)insertedItem["EventStartDateTime"].Controls[0]; //Events start date time  

string strEventStartDateTime = EventStartDateTime.SelectedDate.ToString();  

RadDatePicker EventEndDateTime = (RadDatePicker)insertedItem["EventEndDateTime"].Controls[0]; //Events end date time

string strEventEndDateTime = EventEndDateTime.SelectedDate.ToString();

string CountofEvents = (insertedItem["CountofEvents"].Controls[0] as RadNumericTextBox).Text; //Count of Events

string SalesLinePressure = (insertedItem["SalesLinePressure"].Controls[0] as RadNumericTextBox).Text; //Sales Line Pressure

string ShutInPressure = (insertedItem["ShutInPressure"].Controls[0] as RadNumericTextBox).Text; //Shut In Pressure

string FOpHierarchyID = (insertedItem["FOpHierarchy_ID"].Controls[0] as TextBox).Text; //FOpHierarchy

 }

catch (Exception ex)

 {

RadGrid1.Controls.Add( 

new LiteralControl("Unable to insert Event. Reason: " + ex.Message));

e.Canceled =

true;

}

}

Please assist.
thanks,
Minh Bui