Can't activate activerecord since already activated

=> Booting Mongrel (use ‘script/server webrick’ to force WEBrick)
=> Rails 2.1.2 application starting on http://0.0.0.0:3000
=> Call with -d to detach
=> Ctrl-C to shutdown server
** Starting Mongrel listening at 0.0.0.0:3000
** Starting Rails with development environment…
Exiting
C:/svs/InstantRails-2.0-win/ruby/lib/ruby/site_ruby/1.8/rubygems.rb:319:in
acti vate': can't activate activerecord (= 2.0.2), already activated activerecord-2.1 .2] (Gem::Exception) from C:/svs/InstantRails-2.0-win/ruby/lib/ruby/site_ruby/1.8/rubygems/cu stom_require.rb:31:in require’
from
C:/svs/InstantRails-2.0-win/rails_apps/trunk/vendor/rails/activesup
port/lib/active_support/dependencies.rb:510:in require' from C:/svs/InstantRails-2.0-win/rails_apps/trunk/vendor/rails/activesup port/lib/active_support/dependencies.rb:355:in new_constants_in’
from
C:/svs/InstantRails-2.0-win/rails_apps/trunk/vendor/rails/activesup
port/lib/active_support/dependencies.rb:510:in require' from C:/svs/InstantRails-2.0-win/rails_apps/trunk/vendor/rails/activerec ord/lib/active_record.rb:44 from C:/svs/InstantRails-2.0-win/ruby/lib/ruby/site_ruby/1.8/rubygems/cu stom_require.rb:27:in gem_original_require’
from
C:/svs/InstantRails-2.0-win/ruby/lib/ruby/site_ruby/1.8/rubygems/cu
stom_require.rb:27:in require' from C:/svs/InstantRails-2.0-win/rails_apps/trunk/vendor/rails/activesup port/lib/active_support/dependencies.rb:510:in require’
… 35 levels…
from
C:/svs/InstantRails-2.0-win/rails_apps/trunk/vendor/rails/railties/
lib/commands/server.rb:39
from
C:/svs/InstantRails-2.0-win/ruby/lib/ruby/site_ruby/1.8/rubygems/cu
stom_require.rb:27:in gem_original_require' from C:/svs/InstantRails-2.0-win/ruby/lib/ruby/site_ruby/1.8/rubygems/cu stom_require.rb:27:in require’
from script/server:3

As given i tried “gem cleanup” though it cleaned the already installed
gems it gives the same error as above…

Could anyone help me out???

check installed gems, frozen rails in vendor and environment-entry for
matching version.

which rails version do you intend to use?