MVC :: 404 Error On Ajax Call To Controller

I'm working on getting a new MVC 3.0 application up and running on a Windows 2008 server, running SQL05 and IIS7 with ASP.NET Framwork 4.0 as well as MVC installed. The index page has two select boxes. Selecting an option in the first select box does an ajax call to my controller that populatest the second select box. This works just fine on my winxp dev machine but returns a 404 on the call to the controller when running
on the server. Code for that call:

<% Html.EnableClientValidation(); %>
<% using (Html.BeginForm("CamperDirectory", "TradingPost")) { %>
Select a Season: <%: Html.DropDownListFor(x => x.SelectedSeason, new SelectList(Model.GetSeasons, "Value", "Text"),"Please select a Season.") %><br /><br />
<%: Html.ValidationMessageFor(model => model.SelectedSeason)%>
Select a Session: <%: Html.DropDownListFor(y => y.SelectedSession, new SelectList(Model.GetSessions, "Value", "Text"), "Please select a Summercamp Session.") %>
<%: Html.ValidationMessageFor(model => model.SelectedSession)%>
<input type="submit" value="Go" />
<% } %>
</asp:Content>
<asp:content ID="Content3" contentplaceholderid="HeadContent" runat="server">
<script language="javascript" type="text/javascript">...............................