On a brand new Rails 3 app....

Heroku + json_pure conflict

[~/cool-app (master)]$ bundle install
Fetching source index for http://rubygems.org/
Using rake (0.8.7) 
Using ZenTest (4.4.0) 
Using abstract (1.0.0) 
Using activesupport (3.0.1) 
Using builder (2.1.2) 
Using i18n (0.4.2) 
Using activemodel (3.0.1) 
Using erubis (2.6.6) 
Using rack (1.2.1) 
Using rack-mount (0.6.13) 
Using rack-test (0.5.6) 
Using tzinfo (0.3.23) 
Using actionpack (3.0.1) 
Using mime-types (1.16) 
Using polyglot (0.3.1) 
Using treetop (1.4.9) 
Using mail (2.2.10) 
Using actionmailer (3.0.1) 
Using arel (1.0.1) 
Using activerecord (3.0.1) 
Using activeresource (3.0.1) 
Installing authlogic (2.1.6) 
Using autotest (4.4.4) 
Using autotest-rails (4.1.0) 
Using bundler (1.0.0.rc.5) 
Using configuration (1.2.0) 
Using diff-lcs (1.1.2) 
Using json (1.4.6) 
Using term-ansicolor (1.0.5) 
Using gherkin (2.2.9) 
Using cucumber (0.9.4) 
Using factory_girl (1.3.2) 
Using json_pure (1.4.6) 
Using launchy (0.3.7) 
Using rest-client (1.6.1) 
Using heroku (1.13.7) 
Using nokogiri (1.4.4) 
Using thor (0.14.4) 
Using railties (3.0.1) 
Using rails (3.0.1) 
Using rspec-core (2.1.0) 
Using rspec-expectations (2.1.0) 
Using rspec-mocks (2.1.0) 
Using rspec (2.1.0) 
Using rspec-rails (2.1.0) 
Using sqlite3-ruby (1.3.2) 
Using web-app-theme (0.6.2) 
Using webrat (0.7.2) 
Using wirble (0.1.3) 
Your bundle is complete! Use `bundle show [gemname]` to see where a bundled gem is installed.

Your bundle was installed to `/Users/ben/.rvm/gems/ruby-1.9.2-p0@cool-app`
[~/cool-app (master)]$ rails g
/Users/ben/.rvm/gems/ruby-1.9.2-p0@cool-app/gems/json_pure-1.4.6/lib/json/common.rb:65: warning: already initialized constant State
/Users/ben/.rvm/gems/ruby-1.9.2-p0@cool-app/gems/json_pure-1.4.6/lib/json/common.rb:66: warning: already initialized constant SAFE_STATE_PROTOTYPE
/Users/ben/.rvm/gems/ruby-1.9.2-p0@cool-app/gems/json_pure-1.4.6/lib/json/common.rb:67: warning: already initialized constant FAST_STATE_PROTOTYPE
/Users/ben/.rvm/gems/ruby-1.9.2-p0@cool-app/gems/json_pure-1.4.6/lib/json/common.rb:74: warning: already initialized constant PRETTY_STATE_PROTOTYPE
/Users/ben/.rvm/gems/ruby-1.9.2-p0@cool-app/gems/json_pure-1.4.6/lib/json/ext.rb:14: warning: already initialized constant JSON_LOADED
Usage: rails generate GENERATOR [args] [options]