I have a problem with 2 of my controls "disappearing" when I use the RadAjaxManager to update them when I click a button.

Here is my button:
<asp:Button runat="server" id="btnClick" OnClick="btnClick_Click" />

Here is the btnClick_Click in my C# file:

        protected void btnClick_Click(object sender, EventArgs e)
        {
            SqlConnection myConn3 = new SqlConnection("Dataconnection");
            myConn3.Open();
           
            string getCategoryQueryString;
            getCategoryQueryString = "SELECT MasterTableCategories.MasterID, MasterTableCategories.SICCode, [Sic-Codes].[SIC Name1] AS Category FROM MasterTableCategories INNER JOIN [Sic-Codes] ON MasterTableCategories.SICCode = [Sic-Codes].[SIC Code1] WHERE (MasterTableCategories.MasterID = @MasterID)";

            SqlCommand getCategoryQuery = new SqlCommand(getCategoryQueryString, myConn3);
            getCategoryQuery.Parameters.Add("@MasterID", Master_RecordID.Value);
            SqlDataReader getCategoryReader = getCategoryQuery.ExecuteReader();

            if (getCategoryReader.HasRows)
            {
                getCategoryReader.Read();
                Category.Text = getCategoryReader["Category"].ToString();
                SICCode.Value = getCategoryReader["SICCode"].ToString();
            }
            else
            {
                //For testing purposes
                Category.Text = "Cars";
                SICCode.Value = "123456789";
            }
            getCategoryReader.Dispose();
            myConn3.Close();
        }

Here is the Ajax:
    <telerik:RadAjaxManager ID="RadAjaxManager1" runat="server" DefaultLoadingPanelID="RadAjaxLoadingPanel_CampaignChange">
      <AjaxSettings>
      <telerik:AjaxSetting AjaxControlID="btnClick">
          <UpdatedControls>
            <telerik:AjaxUpdatedControl ControlID="Category" />
            <telerik:AjaxUpdatedControl ControlID="SICCode" />
         </UpdatedControls>
        </telerik:AjaxSetting>
      </AjaxSettings>
    </telerik:RadAjaxManager>

Here are the controls:
<asp:TextBox ID="Category" runat="server" Width="100%" ReadOnly="true"></asp:TextBox>
<asp:HiddenField ID="SICCode" runat="server" Value="" />

The user presses the button and the btnClick_Click goes to the database and retrieves the Category and SIC Code.  It's then supposed to update the controls with string data, but makes the ENTIRE textbox and hidden field disappear from the html.  All I am left with is an empty div...sort of.  It even removes the CategoryPanel div and SICCodePanel div from the html.

If anyone has a clue why these controls vanish, I would appreciate it immensely!