`gem_original_require': no such file to load

i get a cyclic prob using ruby gems , each time i upgrade Ruby and/or
rubygems i get odd errors.

my setup :
Mac OS X 10.4.8
~%> ruby --version
ruby 1.8.5 (2006-08-25) [powerpc-darwin8.8.0]
~%> gem --version
0.9.0

the first error message i got i s when testing Gruff following advices
found in “Cocoa Magic for Gruff Graphs”
http://www.rubycocoa.com/cocoa-magic-for-gruff-graphs

here it is :
~/Desktop/gruff-0.2.4%> ruby
/Users/yvon/Desktop/gruff-0.2.4/test/test_line.rb
opt/local/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:27:in
gem_original_require': no such file to load -- rubycocoa (LoadError) from /opt/local/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:27:inrequire’
from /opt/local/lib/ruby/vendor_ruby/1.8/osx/cocoa.rb:11
from
/opt/local/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:27:in
`gem_original_require’

the second one is under XCode affter a successfull build when the app is
launching (tose apps are suppose to be workable because theyr are
samples coming from
http://www.rubycocoa.com/rubification-central/1#page1 by name
“DOMTreeView” and “Downloader”), bothn of them got the same error
message :

opt/local/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:27:in
gem_original_require': no such file to load -- rubycocoa (LoadError) from /opt/local/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:27:inrequire’
from /opt/local/lib/ruby/vendor_ruby/1.8/osx/webkit.rb:14
from
/opt/local/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:27:in
gem_original_require' from /opt/local/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:27:inrequire’
from
/Users/yvon/work/RubyCocoa/DOMTreeView/build/Release/DOMTreeView.app/Con
tents/Resources/DOMDataSource.rb:12
from
/opt/local/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:27:in
gem_original_require' from /opt/local/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:27:inrequire’
from
/Users/yvon/work/RubyCocoa/DOMTreeView/build/Release/DOMTreeView.app/Con
tents/Resources/rb_main.rb:18:in rb_main_init' from /Users/yvon/work/RubyCocoa/DOMTreeView/build/Release/DOMTreeView.app/Con tents/Resources/rb_main.rb:17:ineach’
from
/Users/yvon/work/RubyCocoa/DOMTreeView/build/Release/DOMTreeView.app/Con
tents/Resources/rb_main.rb:17:in `rb_main_init’
from
/Users/yvon/work/RubyCocoa/DOMTreeView/build/Release/DOMTreeView.app/Con
tents/Resources/rb_main.rb:23

notice also both ruby ans rubycocoa ware installed and upgraded using
darwinports.