Error: no such file to load -- geokit (plugin is install)

Hi,
after spending hours on getting geokit and ym4r running I don't know how
to do or how to getting a test running. I have try the tutorial from
http://www.railslodge.com/plugins/179-ym4r but I don't get it :(.
Has sone one other tutorials he can recommend?

Maybe someone knows were I did my mistake (I only want to show a fixed
address, no database connection so far, pure simplicity :wink: ).

I have installed the plugins Geokit and Ym4r (vendor/plugins). So far I
understood Ym4r require Geokit?
I have no model (no data will be stored).
I have a controller geokittest.

The controller contains:
class GeokittestController < ApplicationController
    require 'geokit'
    require 'ym4r_gm'
    include ym4r_gm::GoogleMaps
    include GeoKit::Geocoders

def index
    @map = GMap.new("map_div")
    @map.control_init(:large_map => true,:map_type => true)
    @map.center_zoom_init([75.5,-42.56],4)
    #@map.overlay_init(GMarker.new([75.6,-42.467],:title => "Hello",
:info_window => "Info! Info!"))
end

75.5,-42.56 should be the data for the map.

In the next step I want to initiate a map.
For this, so far I get it from the tutorial, I have to call the map in
the view via:
<html>
  <head>
        <%= GMap.header %>
  <%= @map.to_html %>
  </head>
  <body>
    <%= @map.div(:width => 600, :height => 400) %>
  </body>
</html>

When I now open the rhtml I got the following error message:
MissingSourceFile in GeokittestController#start
no such file to load -- geokit

What is my mistake? geokit is required and available as plugin in
vendor... and ideas, assumptions or hints :)?