AutoCompleteExtender?

Jag får inte detta att rulla, jag får heller inga fel.
Vad felar?

    <asp:TextBox ID="txtUser" runat="server" CssClass="txtbox" OnTextChanged="FilterChanged" />
                                            <ajaxToolkit:AutoCompleteExtender 
                                                ID="autoComplete" BehaviorID="autoComplete" runat="server"
                                                TargetControlID="txtUser" ServiceMethod="GetCompletionList" 
                                                CompletionSetCount="5" 
                                                MinimumPrefixLength="1" CompletionInterval="1000"
                                                CompletionListCssClass="autocomplete_list" 
                                                CompletionListItemCssClass="autocomplete_listItem" 
                                                CompletionListHighlightedItemCssClass="autocomplete_highlighted_listitem" />

....

    <WebMethod()> _
    <ScriptMethod()> _
        Public Shared Function GetCompletionList(ByVal prefixText As String, ByVal count As Integer) As String()
        Dim list As MembershipUserCollection = Membership.GetAllUsers()
        Dim suggestions As New Generic.List(Of String)()
        For Each s As String In list
            If s.StartsWith(prefixText) Then
                suggestions.Add(s)
            End If
        Next
        suggestions.Add("Kalle")
        Return suggestions.ToArray()
    End Function

Man var tvungen att lägga till System.Web.Script.Services.ScriptService i web-servicen.