Everything was running great in rails 3.0.8. I am upgrading to rails 3.2 eventually but to get things ready Ryan Bates in a Railscast recommends first upgrading to the latest rails 3.0 version which is 3.0.17. After upgrading to 3.0.17 I got:
undefined method `reputation_value_for'
I am running rails in a rvm installed Ruby version 1.9.2. To be sure that it wasn’t a problem with gems, I uninstalled 1.9.2 and reinstalled it. I installed the bundler gem and then ran bundle install. It still got the same error.
I then renamed the database migrations and ran rails g reputation_system. The old and new migration files were exactly the same.
Gist of full backtrace, Gemfile and Gemfile.lock here.
I briefly looked over the code of the gem, can it be that the method you want is now named reputation_for?
it was deprecated and replaced by reputation_for, see commit
https://github.com/twitter/activerecord-reputation-system/commit/552c04b0dead76cd79fb3915845b17b6a8de0cca