UpdatePanel Resetting Object To Inital State?

I have an application that I am currently writing that works by iterating through nodes, and then updating the page with the information of the current node. I have an UpdatePanel in the page which contains a label, textbox, and a button. The label lists the currently available children of the current node, the user enters in which child they want to go to into the textbox, and then hits the submit button. I set the new value of the node in the submit button's event handler.

Here's my problem: Every time I enter in which node I want to navigate to, the object resets its value to the value it was initially initialized to. I have even put this same code into a Windows Form to validate that it's working correctly to iterate through my tree, and it works as it should, so I know my problem is AJAX-related.

This is the first app that I have written using AJAX, so I am still in the process of learning how it works. Here is the HTML:

<form id="form1" runat="server">
<asp:ScriptManager ID="ScriptManager" runat="server"></asp:ScriptManager>
<asp:UpdatePanel ID="UpdatePanel" runat="server" UpdateMode="Conditional">[code]....

current is the current node, which has a public ArrayList of all of its children's IDs. tree is the NodeTree I have; calling Node just returns the new node. Both current and Tree get initialized in the Page_Load event, and that only fires once (when the page is first loaded).It's really pretty simply code; I'm just having difficulty understanding why the AJAX isn't working correctly.