Dhtml Calendar Engine undefined method popup_calendar

Hi,
   I'm trying to use the above engine following the installation here http://dry.4thebusiness.com/DhtmlCalendar.html . The only exception to the install is I downloaded and unzipped the install into the plugins directory from Ruby Forge http://rubyforge.org/projects/dhtmlcalendar/

I'm using Instant Rails and Rails V1.1.6., The engine plugin is also installed

The engine seems to load when I restart WebBrick but the methods are not available in the views.

ActionView::TemplateError (undefined method `popup_calendar' for #<#<Class:0x36b3f10>:0x36b3880>) on line #46 of app/views/release_notes/_form.rhtml:
46: <%= popup_calendar 'release_note', 'date_approved_for_release',
47: { :class => 'date',
48: :field_title => 'Date approved for release',

Anyone have any idea of my mistake?

Thanks and regards

Ross