Rails 3 + Postgre + incompatible character encodings: ASCII-8BIT and UTF-8

Hi friends!
I'm having problems to load some data in a Postgresql database using
"rake db:seed".

/work/arzamas1$ rake db:seed
(in /home/luiz/work/arzamas1)
rake aborted!
incompatible character encodings: ASCII-8BIT and UTF-8

The database was created with these parameters:
CREATE DATABASE arzamas1
  WITH OWNER = postgres
       ENCODING = 'UTF8'
       TABLESPACE = pg_default
       LC_COLLATE = 'pt_BR.utf8'
       LC_CTYPE = 'pt_BR.utf8'
       CONNECTION LIMIT = -1;

This is my database.yml:
development:
  adapter: postgresql
  encoding: utf8
  database: arzamas1
  username: postgres
  password: postgres

This is my gemfile:
source 'http://rubygems.org'
gem 'rails', '3.0.3'
gem 'pg' <---- (0.10.1)
gem 'jquery-rails'
group :development do
  gem 'rspec-rails'
  gem 'annotate-models'
end

The classes related with the problem have the following definition (I
suppressed some parameters for legibility):

try this on the top of you seed.rb:

# -*- coding: utf-8 -*-

Hmmm, I tried but didn't worked.
Thanks for reply!