Can't seem to instantiate Builder::XmlMarkup.new?

I am unable to instantiate the Builder::XmlMarkup.new on one
development machine ( Windows ) and upon my CentOS server. When I run
the same code on my Ubuntu 8.10 VMWare machine, everything runs great?

In the Builder documentation ( http://builder.rubyforge.org/ ) it
shows to put this at the top of the controller;

require ‘rubygems’
require_gem ‘builder’

but this causes the controller to fail when it opens. I’ve locally
installed the ‘Builder’ gem although this doesn’t exist in my Linux
stack and runs fine. Here’s the details on the GEM I installed;
gem = “Builder” by [email protected] at http://onestepback.org/

Does ActiveRecord ( as of 2.2.2 ) now have this feature? If so, why
can’t my controller create an instance of this class?

David