RadAjaxPanel ajaxRequest doesn't update

[Ravi]

Hi,
I have a page with tabstrip and multipage control which each holds a user controls

<telerik:RadStrip..>
      <Tabs>
            <telerik:RadTab Text="Image" PageViewID="PageViewImage" ... />
</telerik:RadStrip>

<telerik:RadMultiPage ... .>
<telerik:RadPageView ...>
                 <uc1:ImageChanger id.. />
         </telerik:RadPageView>
</telerik:RadMultiPage>

User Control: ImageChanger.ascx
<script language="javascript" ..>
      function OpenImageChanger(){ 
         ...
         // Opens a rad window.. 
        oWindow.add_close(RefreshImage)
      }
   
     function RefreshImage(){
$find("<%= AjaxPanelID.ClientID %>").ajaxRequest('');
    }
</script>
<telerik:RadAjaxPanel ... OnAjaxRequest="Imager_AjaxRequst" ..
           <asp:Image id="ImgCover" runat="server" ImageUrl="default.jpg" />
</teleirk:RadJaxPanel>
<input type="button" onclik="OpenImageChanger()" />

Code Behind: ImageChanger.ascx.cs
protected void Imager_AjaxRequest(object sender, AjaxRequestEventArgs e){
imgCover.ImageUrl = newImage
}


I have put a break point and I do see that the AjaxRequest Event is executed but nothing really changed at the client side.  The Image was still at default.  Also I followed the same approach where another tab and another user control which has treeview.  That treeview didn't get updated as well.  Please advise if I am missing anything since it's being a road block for me to go further.  

Thanks,