facebooker error ?

I installed the facebooker plugin and now I'm getting this error but not sure what it means...

/usr/local/lib/site_ruby/1.8/rubygems/custom_require.rb:27:in `gem_original_require': no such file to load -- json (MissingSourceFile) from /usr/local/lib/site_ruby/1.8/rubygems/ custom_require.rb:27:in `require' from /usr/lib/ruby/gems/1.8/gems/ activesupport-2.0.2/lib/active_support/dependencies.rb:496:in `require' from /usr/lib/ruby/gems/1.8/gems/activesupport-2.0.2/lib/ active_support/dependencies.rb:342:in `new_constants_in' from /usr/lib/ ruby/gems/1.8/gems/activesupport-2.0.2/lib/active_support/ dependencies.rb:496:in `require' from /mnt/home/userapps/11561/vendor/ plugins/facebooker/lib/facebooker.rb:1 from /usr/local/lib/site_ruby/ 1.8/rubygems/custom_require.rb:27:in `gem_original_require' from /usr/ local/lib/site_ruby/1.8/rubygems/custom_require.rb:27:in `require' from /usr/lib/ruby/gems/1.8/gems/activesupport-2.0.2/lib/ active_support/dependencies.rb:496:in `require' ... 23 levels... from / usr/lib/ruby/gems/1.8/gems/rails-2.0.2/lib/commands/generate.rb:1 from /usr/local/lib/site_ruby/1.8/rubygems/custom_require.rb:27:in `gem_original_require' from /usr/local/lib/site_ruby/1.8/rubygems/ custom_require.rb:27:in `require' from script/generate:3