The server method "[webmethod name]" failed

[Dave]

**** Disregard, I've found the issue:  The asmx page was not pointing to the correct class.******

I can't get your combo to populate from web service and the error message is useless.  It does not even appear to call the webmethod. 

ascx

<telerik:RadComboBox ID="rcbRevenueType" EnableVirtualScrolling="true" EnableViewState="false"
                        AllowCustomText="true" ShowMoreResultsBox="false" ShowToggleImage="true" EnableItemCaching="true"
                        MaxHeight="150px" MarkFirstMatch="True" ChangeTextOnKeyBoardNavigation="true" EnableScreenBoundaryDetection="true"
                        EnableTextSelection="true" ShowDropDownOnTextboxClick="true" ShowWhileLoading="true"
                        runat="server" EnableLoadOnDemand="true" EnableEmbeddedSkins="false" Skin="CienaComboBox"
                        Width="200px">
                        <CollapseAnimation Duration="200" Type="OutQuint" />
                        <WebServiceSettings Path="~/DataLookupService.asmx" Method="GetAllRevenueTypes" />
                    </telerik:RadComboBox>

asmx.cs

[WebMethod]
        public RadComboBoxData GetAllRevenueTypes(RadComboBoxContext context)
        {
            LookupDAO lookup = new LookupDAO();
            DataTable dt = lookup.GetActiveRevenueTypesDT();
            DataView dv = dt.DefaultView;
            dv.Sort = "Name ASC";
            return FormatItems(dv, context, "Name", "RevenueType_ID", 8);

        }

        public RadComboBoxData FormatItems(DataView dv, RadComboBoxContext context, string text, string value, int requestcount)
        {
            List<RadComboBoxItemData> result = null;
            // Create a RadComboBoxData object to pass virtual scrolling information
            RadComboBoxData comboData = new RadComboBoxData();
            // calculate the number of records we need
            // based on the current number of items
            int itemsPerRequest = requestcount;
            int itemOffset = context.NumberOfItems;
            int endOffset = itemOffset + itemsPerRequest;
            // adjust endOffset if there are not enough rows
            if (endOffset > dv.Count)
            {
                endOffset = dv.Count;
            }
            // set EndOfItems to reflect whether we are supplying the last items
            if (endOffset == dv.Count)
            {
                comboData.EndOfItems = true;
            }
            else
            {
                comboData.EndOfItems = false;
            }
            // create the list to hold the items we will return
            result = new List<RadComboBoxItemData>(endOffset - itemOffset);
            // iterate through the rows of the table, creating and adding items
            for (int i = itemOffset; i < endOffset; i++)
            {
                RadComboBoxItemData itemData = new RadComboBoxItemData();
                itemData.Text = dv[i][text].ToString();
                itemData.Value = dv[i][value].ToString();
                result.Add(itemData);
            }
            comboData.Items = result.ToArray();
            return comboData;

        }