Redmine

I installed graph plug-in (redmine 0.8.3) and got this error below.
Any suggestions on what is wrong?
Thanks. Antoine.

Log :

Processing GraphsController#issue_growth_graph (for 127.0.0.1 at 2009-05-14 11:41:08) [GET]
Session ID: 63c3b655dac2bbc7a8ba26db283dcdb8
Parameters: {"project_id"=>"1", "action"=>"issue_growth_graph", "controller"=>"graphs"}

NameError (undefined local variable or method `transitive' for <UNDEFINED> ... :REXML::Document):
c:/ruby/lib/ruby/1.8/rexml/document.rb:186:in `write'
/lib/SVG/Graph/Graph.rb:211:in `burn'
/vendor/plugins/redmine_graphs/app/controllers/graphs_controller.rb:135:in `issue_growth_graph'
/vendor/rails/actionpack/lib/action_controller/base.rb:1166:in `send'
/vendor/rails/actionpack/lib/action_controller/base.rb:1166:in `perform_action_without_filters'
/vendor/rails/actionpack/lib/action_controller/filters.rb:579:in `call_filters'
/vendor/rails/actionpack/lib/action_controller/filters.rb:572:in `perform_action_without_benchmark'
/vendor/rails/actionpack/lib/action_controller/benchmarking.rb:68:in `perform_action_without_rescue'
c:/ruby/lib/ruby/1.8/benchmark.rb:293:in `measure'
/vendor/rails/actionpack/lib/action_controller/benchmarking.rb:68:in `perform_action_without_rescue'
/vendor/rails/actionpack/lib/action_controller/rescue.rb:201:in `perform_action_without_caching'
/vendor/rails/actionpack/lib/action_controller/caching/sql_cache.rb:13:in `perform_action'
/vendor/rails/activerecord/lib/active_record/connection_adapters/abstract/query_cache.rb:33:in `cache'
/vendor/rails/activerecord/lib/active_record/query_cache.rb:8:in `cache'
/vendor/rails/actionpack/lib/action_controller/caching/sql_cache.rb:12:in `perform_action'
/vendor/rails/actionpack/lib/action_controller/base.rb:529:in `send'
/vendor/rails/actionpack/lib/action_controller/base.rb:529:in `process_without_filters'
/vendor/rails/actionpack/lib/action_controller/filters.rb:568:in `process_without_session_management_support'
/vendor/rails/actionpack/lib/action_controller/session_management.rb:130:in `process'
/vendor/rails/actionpack/lib/action_controller/base.rb:389:in `process'
/vendor/rails/actionpack/lib/action_controller/dispatcher.rb:149:in `handle_request'
/vendor/rails/actionpack/lib/action_controller/dispatcher.rb:107:in `dispatch'
/vendor/rails/actionpack/lib/action_controller/dispatcher.rb:104:in `synchronize'
/vendor/rails/actionpack/lib/action_controller/dispatcher.rb:104:in `dispatch'
/vendor/rails/actionpack/lib/action_controller/dispatcher.rb:120:in `dispatch_cgi'
/vendor/rails/actionpack/lib/action_controller/dispatcher.rb:35:in `dispatch'
/vendor/rails/railties/lib/webrick_server.rb:112:in `handle_dispatch'
/vendor/rails/railties/lib/webrick_server.rb:78:in `service'
c:/ruby/lib/ruby/1.8/webrick/httpserver.rb:104:in `service'
c:/ruby/lib/ruby/1.8/webrick/httpserver.rb:65:in `run'
c:/ruby/lib/ruby/1.8/webrick/server.rb:173:in `start_thread'
c:/ruby/lib/ruby/1.8/webrick/server.rb:162:in `start'
c:/ruby/lib/ruby/1.8/webrick/server.rb:162:in `start_thread'
c:/ruby/lib/ruby/1.8/webrick/server.rb:95:in `start'
c:/ruby/lib/ruby/1.8/webrick/server.rb:92:in `each'
c:/ruby/lib/ruby/1.8/webrick/server.rb:92:in `start'
c:/ruby/lib/ruby/1.8/webrick/server.rb:23:in `start'
c:/ruby/lib/ruby/1.8/webrick/server.rb:82:in `start'
/vendor/rails/railties/lib/webrick_server.rb:62:in `dispatch'
/vendor/rails/railties/lib/commands/servers/webrick.rb:66
c:/ruby/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:27:in `gem_original_require'
c:/ruby/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:27:in `require'
/vendor/rails/activesupport/lib/active_support/dependencies.rb:510:in `require'
/vendor/rails/activesupport/lib/active_support/dependencies.rb:355:in `new_constants_in'
/vendor/rails/activesupport/lib/active_support/dependencies.rb:510:in `require'
/vendor/rails/railties/lib/commands/server.rb:39
c:/ruby/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:27:in `gem_original_require'
c:/ruby/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:27:in `require'
script/server:3

Rendering C:/ruby/redmine/vendor/rails/actionpack/lib/action_controller/templates/rescues/layout.erb (internal_server_error)