I am receiving this "is not a function error" error, and I can not work out why this is happening. It is no doubt for some simple reason, and I am so close to the code I am overlooking it.

I am including the following jQuery (the last <script> tag is the plugin that isn't working for me):
Code JavaScript:
<script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/jquery/1.4.2/jquery.min.js"></script>
    <script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/jqueryui/1.8.2/jquery-ui.min.js"></script>
<link href="http://ajax.googleapis.com/ajax/libs/jqueryui/1.8/themes/base/jquery-ui.css" rel="stylesheet" type="text/css"/>
        <script src="http://www.jankoatwarpspeed.com/examples/webform_to_wizard/formToWizard.js" type="text/javascript"></script>
(Once I get this working I will be including this plugin file locally)

later in my jquery embeded in my webpage I have a function call:
Code JavaScript:
$(document).ready(function() {	
$("#gform_1").formToWizard({ submitButton: 'submitbutton' });

However, with this, I am getting the error:
Error: $("#gform_1").formToWizard is not a function
Source File: http://localhost/...
Line: 76

But, this function is defined within:

Also I do have a gform_1 in my code:
Code HTML4Strict:
<form method='post' enctype='multipart/form-data' id='gform_1' class='multiform' action=''>....</form>
Any ideas as to what may be the problem?

Many thanks.