Cascading Comboboxes To Work - Getting Method Error 500

I am trying to get my cascading comboboxes to work, but am getting a [Method error 500]. Any ideas? I've searched online, the code should work....Thanks in advance for your help!

ADDSTORY.ASPX:

<%@ Page Language="C#" AutoEventWireup="true" CodeFile="addstory.aspx.cs" Inherits="addstory" %>
<%@ Register Assembly="AjaxControlToolkit" Namespace="AjaxControlToolkit" TagPrefix="asp" %>
<form id="form1" runat="server">
<asp:ToolkitScriptManager ID="ScriptManager1" runat="server" />
<td class="style3">
<asp:DropDownList ID="selectproject" runat="server" Width="225"></asp:DropDownList>
<asp:CascadingDropDown ID="ccd1" runat="server"
ServicePath="~/dropdown.asmx?company=<%=co_id %>" ServiceMethod="GetProjects"
TargetControlID="selectproject" Category="Project"
PromptText="Select Project" />
</td>
</tr>
<tr>
<td class="style3"></td>
<td width = "150" class="style3">Iteration:</td>
<d class="style3">
<asp:DropDownList ID="selectiteration" runat="server" Width="225"></asp:DropDownList>
<asp:CascadingDropDown ID="ccd2" runat="server"
ServicePath="~/dropdown.asmx?company=<%=co_id %>" ServiceMethod="GetIterations"
TargetControlID="selectiteration" Category="Iteration"
PromptText="Select Iteration" />
</td>
</tr>
DROPDOWN.ASMX:
using System.Web.Script.Services;
using AjaxControlToolkit;
using System;
using System.Web;
using System.Web.Services;
using System.Web.Services.Protocols;
using System.Collections.Generic;
using System.Collections.Specialized;
using System.Data.SqlClient;
/// <summary>
/// Summary description for WebService
/// </summary>
[WebService(Namespace = "[URL]/")]
[WebServiceBinding(ConformsTo = WsiProfiles.BasicProfile1_1)]
// To allow this Web Service to be called from script, using ASP.NET AJAX, uncomment the following line.
[System.Web.Script.Services.ScriptService()]
public class dropdown : System.Web.Services.WebService
{
private string GetConnectionString()
{
return System.Configuration.ConfigurationManager.ConnectionStrings["MyConnection"].ConnectionString;
}
[WebMethod]
public CascadingDropDownNameValue[] GetProjects(string knownCategoryValues, string category)
{
string co_id = this.Context.Request.QueryString["company"].ToString();
SqlConnection conn = new SqlConnection(GetConnectionString());
sonn.Open();
SqlCommand comm = new SqlCommand("Select ProjectName, ProjectID FROM Project WHERE CompanyID = '" + co_id + "'", conn);
SqlDataReader dr = comm.ExecuteReader();
List<CascadingDropDownNameValue> l = new List<CascadingDropDownNameValue>();
while (dr.Read())
{
l.Add(new CascadingDropDownNameValue(dr["ProjectName"].ToString(), dr["ProjectID"].ToString()));
}
conn.Close();
return l.ToArray();
}
[WebMethod]
public CascadingDropDownNameValue[] GetIterations(string knownCategoryValues, string category)
{
int ProjectID;
StringDictionary kv = CascadingDropDown.ParseKnownCategoryValuesString(knownCategoryValues);
if (!kv.ContainsKey("Project") || !Int32.TryParse(kv["Project"], out ProjectID))
{
throw new ArgumentException("Couldn't find project.");
};
SqlConnection conn = new SqlConnection(GetConnectionString());
conn.Open();
SqlCommand comm = new SqlCommand("SELECT Select CONVERT(VARCHAR(10), StartDate, 103) + ' - ' + CONVERT(VARCHAR(10), EndDate, 103) AS Iteration, ProjectIterationID FROM Iterations WHERE ProjectID=@ProjectID", conn);
comm.Parameters.AddWithValue("@ProjectID", ProjectID);
SqlDataReader dr = comm.ExecuteReader();
List<CascadingDropDownNameValue> l = new List<CascadingDropDownNameValue>();
while (dr.Read())
{
l.Add(new CascadingDropDownNameValue(dr["Iteration"].ToString(), dr["ProjectIterationID"].ToString()));
}
conn.Close();
return l.ToArray();
}
}