Usercontrol postback not working in updatepanel

I have a home page with an update panel:

<asp:UpdatePanel ID="UpdatePanel" runat="server" ChildrenAsTriggers="true" EnableViewState="False"
                UpdateMode="Conditional">
                <ContentTemplate>
                    <div id="mainContent">
                        <asp:ContentPlaceHolder ID="ContentPlaceHolder1" runat="server">
                        </asp:ContentPlaceHolder>
                    </div>
                </ContentTemplate>
                <Triggers>
              </Triggers>
            </asp:UpdatePanel>

      

        
        
        
      

    

Then I have a Default.aspx page that uses the main page file:

<asp:Content ID="Content1" runat="server" ContentPlaceHolderID="ContentPlaceHolder1">
<asp:PlaceHolder ID="plhCurrentItem" runat="server"></asp:PlaceHolder>
</asp:Content>

      

        
        
        
      

    

I am loading usercontrols programmatically into placeholder with id plhCurrentItem.

The problem is when I click the button in the usercontrol, no event is fired. The user control simply disappears and the updated panel remains blank.

What am I doing wrong?

Update

Code used to add usercontrols. The LoadControls method is called from the Page_load event.

 Control ctlCurrentItem = null;

public string currentControl
{
    get { return ((string)Session["currentControl"]); }
    set { Session["currentControl"] = value; }
}



public void LoadControls()
{
    switch (currentControl)
    {
        case "Home":
            ctlCurrentItem = Page.LoadControl("~/pages/Home.ascx");
            ctlCurrentItem.ID = "Home";
            break;
        case "Resume":
            ctlCurrentItem = Page.LoadControl("~/pages/Resume.ascx");
            ctlCurrentItem.ID = "Resume";
            break;
        case "Projects":
            ctlCurrentItem = Page.LoadControl("~/pages/Projects.ascx");
            ctlCurrentItem.ID = "Projects";
            break;
        case "Contact":
            ctlCurrentItem = Page.LoadControl("~/pages/Contact.ascx");
            ctlCurrentItem.ID = "Contact";
            break;
        default:
            return;

    }
    plhCurrentItem.Controls.Clear();
    plhCurrentItem.Controls.Add(ctlCurrentItem);


}