Can you reproduce this error?

Generate a model with a property named 'y' of any type. You should end
up with a migration something like this:

class CreateYTests < ActiveRecord::Migration
  def self.up
    create_table :y_tests do |t|

      t.integer :y
    end
  end

  def self.down
    drop_table :y_tests
  end
end

Then try to run YTest.new.to_xml and YTest.new.to_json in the console.

They should error and YTest.to_yaml should not error. Do they?

See:

http://dev.rubyonrails.org/ticket/9797