Mandriva 2010.1, ruby 1.8.7, gem 1.4.1

A few months ago I installed the OptionParser gem and have been using
it successfully until a gem update --system.  Now the interpreter
cannot locate the directories containing the gem.

Script header:
---------------------------------------------------------------------
#!/usr/bin/env ruby
require 'rubygems'
require 'commandline/optionparser'
include CommandLine
require 'tk'
---------------------------------------------------------------------
error:
/usr/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:29:in
`gem_original_require': no such file to load --commandline/optionparser 
(LoadError)

An experiment with
require
'/usr/lib/ruby/gems/1.8/gems/OptionParser-0.5.1/lib/commandline/
optionparser'
raised similar errors on the files required by optionparser.rb which were
commandline/optionparser/option and commandline/optionparser/optiondata.

I don't know how to proceed from here.  Looks like the default search
paths have been affected by the update of rubygems.  ??

At the command line puts $LOAD_PATH gives undefined variable.  In irb
the require 'commandline/optionparser' fails as expected and a puts
"#{LOAD_PATH}" reports uninitialized constant.  I have never had to
set the LOAD_PATH in the past.  Has something changed with gem 1.4.1?
What I have noticed is that the one gem installed after the update
appears by itself in a newly created /usr/lib64/ruby/gems/1.8/gems.

Happy new Year

Len