Error: No plugin called...

Hi everyone,

I'm desperatelly trying to install the "datetime_toolbocks" plugin, and
for a 2nd day now I can't figure out what I'm doing wrong.

I have InstantRails with Rails 2.1.1 and Engines 2.1.0. The
datetime_toolbocks plugin is also installed, and following the
instructions of this plugin, I am supposed to add the following lines
within the application's layout:

  <%= stylesheet_link_tag 'datetime_toolbocks', 'calendar-blue', :plugin
=> 'datetime_toolbocks' %>
  <%= javascript_include_tag 'prototype' %>
  <%= javascript_include_tag 'datetime_toolbocks', 'calendar',
'lang/calendar-en', 'calendar-setup', :plugin => 'datetime_toolbocks' %>

The server starts without any problem, but my browser gives me:

No plugin called 'datetime_toolbocks' - please use the full name of a
loaded plugin.

The plugin is installed under

...and if I get rid of those 3 lines in the application's layout,
there's no problem.

Please help, I'm stuck with this plugin for a whole week now.