UpdatePanel not working in IE or Chrome

Question

I have an updatepanel on my masterpage. Within the contentplace holder I have my update progress control. When a user clicks on the button I load some data into a gridview. This works perfectly in FireFox. User clicks the button, the loading image in my updateprogress fires and loads the gridview. When I test this in IE 6 or 7 or in Chrome. It does a full postback and the updateprogress is never shown. So the updatepanel doesnt seem to be working in these two browsers. Code is below. Again...it works perfect in FireFox.

***From Masterpage ***

<asp:UpdatePanel ID="UpdatePanel" runat="server">
 <contenttemplate>
  <asp:contentplaceholder id="holder" runat="server" />
  </contenttemplate>
</asp:UpdatePanel>

**From aspx page ****

 <asp:UpdateProgress ID="UpdateProgress1" runat="server">
    <ProgressTemplate>
       <img src="ajax-loader.gif" />
    </ProgressTemplate>
 </asp:UpdateProgress>