Newbie: AJAX not working - Undefined Method error

Hello

I have included prototype in my Applications rhtml file
<head>
     <%= javascript_include_tag "prototype" %>
    <title>FLYPRO </title>
     <%= stylesheet_link_tag 'flypro' %>
</head>

I call link_to_remote in a page as follows

<div id="flypro-list">
</div>
<%= link_to_remote("Do Something",
                  :update => 'flypro-list',
                  :url => { :action => :list})%>

But when I hit the Link I get undefined method `link_to_remote' for
#<#<Class:0x3706090>:0x3706054

The translated page viewed as source, has translated link_to_remote
into

<a href="#" onclick="new Ajax.Updater('flypro-list', '/flypro/list',
{asynchronous:true, evalScripts:true}); return false;">Do Something</

This looks OK, so I don't understand why I get undefined method error
on "periodcally_call_remote", when it should be hooking up to
Ajax.updater, which does exist in prototype ? prototype does exist
under the public/javascripts folder.

Am I using the wrong prototype.js ? I cannot find any 'link_to_remote'
functions in prototype.js, so where is it defined ?

Any help appreciated

Thanks

Julian