Class is not defined error with presto-connect.js

I'm trying to do a simple invocation of a service published in Presto Mashup Server. When the javascript modules are loaded I get the exception:

Class is not defined presto-connect.js()() presto-connect.js (line 618) Presto.DataProxy = Class.create({

When I try to create the Presto connection I get the following exception: Object.extend is not a function" coming from line 148 of presto-connect.js.

I put the following in my HTML as instructed in the documentation.

<script language="javascript" src="http://localhost:8080/static/common/js/prototype-1.6.0.js"></script> <script language="JavaScript" src="http://localhost:8080/static/common/js/presto-utils.js"></script> <script language="JavaScript" src="http://localhost:8080/static/common/js/presto-connect.js"></script>

My Javascript looks like this:

function getData(wordRoot)
{
    try
    {
      var prestoUrl = "http://127.0.0.1:8080/presto";
      var connection = new Presto.Connection({prestoUrl: prestoUrl, username: 'xxx', password: 'xxx'});
    }
    catch (e)
    {
        console.error(e);
    }
    connection.request(
          { //request configuration
              sid: 'SpellSuggest',
              oid: 'getData',

              //input parameters
              params: {
                  "wordRoot":wordRoot,
                  "size":10
              }
          },
          { //callback
              onSuccess: function(response) {
                  console.log('response = ');
                  console.log(data.response);
                  alert('success');
              },
              onFailure: function(err) {
                  alert('failure = ' + err.message);
              },
              scope: this
          }
    );
    console.log("done");
 }

any ideas? Thanks!