pagemethods returns html string (from masterpage?)

Hi,

I have managed to set up a call to a function in codebehind through pagemethods. It return a success but instead of the test string (Hello) it returns a html string that seems to be a small part of the masterpage. What am I missing/doing wrong?

    function ShowCurrentTime() {
            PageMethods.Hello(Success, Failure);
    }

    function Success(result) {
        alert(result);
    }
    function Failure(error) {
        alert(error);
    }

code behind:

<WebMethod()>
    Public Shared Function Hello() As String
        Dim SayHello As String = "Hello"
        Return SayHello
    End Function

Thanks in advance,

Pascal