Redmine

I'm trying to install redmine-1.1.3.
And when I tried to do "rake generate_session_store",
error msg below is shown.

My environment is belows.
- ruby-1.8.7-p334
- rails 2.3.5
- rubygems-1.8.3
- AIX 6.1.0.0
- mysql-5.1.55

Pls help me how to figure out this problem.
---------------------------------------------------------------
Gem::SourceIndex#add_spec called from /usr/local/ruby/lib/ruby/site_ruby/1.8/rubygems/source_index.rb:91.
NOTE: Gem::SourceIndex#add_spec is deprecated, use Specification.add_spec. It will be removed on or after 2011-11-01.
Gem::SourceIndex#add_spec called from /usr/local/ruby/lib/ruby/site_ruby/1.8/rubygems/source_index.rb:91.
NOTE: Gem::SourceIndex#add_spec is deprecated, use Specification.add_spec. It will be removed on or after 2011-11-01.
Gem::SourceIndex#add_spec called from /usr/local/ruby/lib/ruby/site_ruby/1.8/rubygems/source_index.rb:91.
NOTE: Gem::SourceIndex#add_spec is deprecated, use Specification.add_spec. It will be removed on or after 2011-11-01.
Gem::SourceIndex#add_spec called from /usr/local/ruby/lib/ruby/site_ruby/1.8/rubygems/source_index.rb:91.
rake/rdoctask is deprecated. Use rdoc/task instead (in RDoc 2.4.2+)

rake aborted!
no such file to load -- active_support

/usr/local/ruby/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:59:in `gem_original_require'
/usr/local/ruby/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:59:in `require'
/tx/redmine-1.1.3/vendor/rails/railties/lib/tasks/misc.rake:18
/tx/redmine-1.1.3/vendor/rails/railties/lib/tasks/rails.rb:4:in `load'
/tx/redmine-1.1.3/vendor/rails/railties/lib/tasks/rails.rb:4
/tx/redmine-1.1.3/vendor/rails/railties/lib/tasks/rails.rb:4:in `each'
/tx/redmine-1.1.3/vendor/rails/railties/lib/tasks/rails.rb:4
/usr/local/ruby/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:36:in `gem_original_require'
/usr/local/ruby/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:36:in `require'
/tx/redmine-1.1.3/Rakefile:10
/usr/local/ruby/lib/ruby/gems/1.8/gems/rake-0.9.0/lib/rake/rake_module.rb:25:in `load'
/usr/local/ruby/lib/ruby/gems/1.8/gems/rake-0.9.0/lib/rake/rake_module.rb:25:in `load_rakefile'
/usr/local/ruby/lib/ruby/gems/1.8/gems/rake-0.9.0/lib/rake/application.rb:495:in `raw_load_rakefile'
/usr/local/ruby/lib/ruby/gems/1.8/gems/rake-0.9.0/lib/rake/application.rb:78:in `load_rakefile'
/usr/local/ruby/lib/ruby/gems/1.8/gems/rake-0.9.0/lib/rake/application.rb:129:in `standard_exception_handling'
/usr/local/ruby/lib/ruby/gems/1.8/gems/rake-0.9.0/lib/rake/application.rb:77:in `load_rakefile'
/usr/local/ruby/lib/ruby/gems/1.8/gems/rake-0.9.0/lib/rake/application.rb:61:in `run'
/usr/local/ruby/lib/ruby/gems/1.8/gems/rake-0.9.0/lib/rake/application.rb:129:in `standard_exception_handling'
/usr/local/ruby/lib/ruby/gems/1.8/gems/rake-0.9.0/lib/rake/application.rb:59:in `run'
/usr/local/ruby/lib/ruby/gems/1.8/gems/rake-0.9.0/bin/rake:31
/usr/local/ruby/bin/rake:19:in `load'
/usr/local/ruby/bin/rake:19