acts_as_taggable Rails 2.0

Helleo,

I'm currently in trouble with acts_as_taggable, indeed, the system
raises this kind of error in Rail 2.0.2. But this works with Rails
1.2.3.

I do not know how to fix it. It seems that something is connected to
the Rails version.

have you hot any clues about what the problem could be?

Thanks in advance.

Arte_fact

NameError (undefined local variable or method `acts_as_taggable' for
Book:Class):
    /var/lib/gems/1.8/gems/activerecord-1.15.3/lib/active_record/
base.rb:1235:in `method_missing'
    /app/models/book.rb:2
    /usr/lib/ruby/1.8/rubygems/custom_require.rb:27:in
`gem_original_require'
    /usr/lib/ruby/1.8/rubygems/custom_require.rb:27:in `require'
    /var/lib/gems/1.8/gems/activesupport-1.4.2/lib/active_support/
dependencies.rb:495:in `require'
    /var/lib/gems/1.8/gems/activesupport-1.4.2/lib/active_support/
dependencies.rb:342:in `new_constants_in'
    /var/lib/gems/1.8/gems/activesupport-1.4.2/lib/active_support/
dependencies.rb:495:in `require'
    /var/lib/gems/1.8/gems/activesupport-1.4.2/lib/active_support/
dependencies.rb:104:in `require_or_load'
    /var/lib/gems/1.8/gems/activesupport-1.4.2/lib/active_support/
dependencies.rb:248:in `load_missing_constant'
    /var/lib/gems/1.8/gems/activesupport-1.4.2/lib/active_support/
dependencies.rb:452:in `const_missing'
    /var/lib/gems/1.8/gems/activesupport-1.4.2/lib/active_support/
dependencies.rb:464:in `const_missing'
    /var/lib/gems/1.8/gems/activesupport-1.4.2/lib/active_support/
inflector.rb:250:in `constantize'
    /var/lib/gems/1.8/gems/activesupport-1.4.2/lib/active_support/
core_ext/string/inflections.rb:148:in `constantize'
    /var/lib/gems/1.8/gems/actionpack-1.13.3/lib/action_controller/
pagination.rb:195:in `paginator_and_collection_for'
    /var/lib/gems/1.8/gems/actionpack-1.13.3/lib/action_controller/
pagination.rb:130:in `paginate'
    /app/controllers/admin/publisher_controller.rb:90