I would compare how you are hooking things up for your update panel to how I did it in BlogEdit.aspx.cs
I'm ajaxifying my button click like this:
if (ScriptController != null)
{
ScriptController.RegisterAsyncPostBackControl(btnAddCategory);
}
ScriptController is just aproperty that gets a reference to ScriptManager from master page:
public ScriptManager ScriptController
{
get
{
if (scriptController == null)
{
scriptController = (ScriptManager)Master.FindControl("ScriptManager1");
}
return scriptController;
}
}
My Update panel is declared like this:
<asp:UpdatePanel ID="UpdatePanel1" UpdateMode="Conditional" runat="server">
I would examine your code and my code in the BlogEdit.aspx.cs and see if you can find substantial differences.
The problem could be because you want to update on panel from another one. I would try doing it all in one update panel.
Hope it helps,
Joe