Bigrecord gem problem

i am facing a problem in using Bigrecord gem. i have my application written in these versions rails-2.1.2,ruby version1.8.7,gems version1.4.2 and i am currently using these versions ruby version=1.8.7, ruby gems=1.4.2, rails version=2.2.3
now the requirement has come on Hbase to store the dynamic data.i installed Bigrecord gem and then entered the same in environment.rb file like this
config.gem "oauth" config.gem "oauth-plugin" config.gem "hpricot" config.gem "htmldoc" config.gem "bigrecord", :source => "http://gemcutter.org" and saved too.

but i am getting some error and i am unable to solve and figure it out.Kindly help me and it is some sort of urgency
error:
[root]# script/generate bigrecord

/usr/local/lib/ruby/site_ruby/1.8/rubygems.rb:232:in activate': undefined methodmap' for nil:NilClass (NoMethodError)

    from /usr/local/lib/ruby/site_ruby/1.8/rubygems.rb:258:in `activate'
    from /usr/local/lib/ruby/site_ruby/1.8/rubygems.rb:257:in `each'
    from /usr/local/lib/ruby/site_ruby/1.8/rubygems.rb:257:in `activate'
    from /usr/local/lib/ruby/site_ruby/1.8/rubygems.rb:1146:in `gem'
    from ./script/../config/../vendor/rails/railties/lib/rails/gem_dependency.rb:36:in `add_load_paths'
    from ./script/../config/../vendor/rails/railties/lib/initializer.rb:245:in `add_gem_load_paths'
    from ./script/../config/../vendor/rails/railties/lib/initializer.rb:245:in `each'
    from ./script/../config/../vendor/rails/railties/lib/initializer.rb:245:in `add_gem_load_paths'
    from ./script/../config/../vendor/rails/railties/lib/initializer.rb:116:in `process'
    from ./script/../config/../vendor/rails/railties/lib/initializer.rb:97:in `send'
    from ./script/../config/../vendor/rails/railties/lib/initializer.rb:97:in `run'
    from /home/passport/knome/knome/config/environment.rb:22
    from /usr/local/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:29:in `gem_original_require'
    from /usr/local/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:29:in `require'
    from /home/passport/knome/knome/vendor/rails/railties/lib/commands/generate.rb:1
    from /usr/local/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:29:in `gem_original_require'
    from /usr/local/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:29:in `require'