Redmine

Hello

Every time I'm trying to open settings tab / my profile tab / creating new user - it sends internal error with this output:

Started GET "/my/account" for ::1 at 2014-11-12 19:19:46 +0100
Processing by MyController#account as HTML
Current user: admin (id=1)
Rendered my/account.html.erb within layouts/base (5.7ms)
Completed 500 Internal Server Error in 13.1ms

ActionView::Template::Error (undefined method `exists?' for I18n:Module):
17: <p><%= f.text_field :lastname, :required => true ></p>
18: <p><= f.text_field :mail, :required => true ></p>
19: < unless @user.force_default_language? >
20: <p><= f.select :language, lang_options_for_select ></p>
21: < end >
22: < if Setting.openid? >
23: <p><= f.text_field :identity_url %></p>
lib/redmine/i18n.rb:98:in `block in languages_options'
lib/redmine/i18n.rb:97:in `select'
lib/redmine/i18n.rb:97:in `languages_options'
lib/redmine/i18n.rb:103:in `block in languages_options'
lib/redmine/i18n.rb:102:in `languages_options'
app/helpers/application_helper.rb:1041:in `lang_options_for_select'
app/views/my/account.html.erb:20:in `block in app_views_my_account_html_erb__2991880112951114304_42193560'
app/helpers/application_helper.rb:1056:in `labelled_form_for'
app/views/my/account.html.erb:9:in `_app_views_my_account_html_erb___2991880112951114304_42193560'

and script/about output

sh: darcs: command not found
sh: hg: command not found
sh: bzr: command not found
Environment:
Redmine version 2.6.0.stable
Ruby version 1.9.3-p550 (2014-10-27) [x86_64-linux]
Rails version 3.2.19
Environment production
Database adapter MySQL
SCM:
Subversion 1.6.11
Git 1.7.1
Filesystem
Redmine plugins:
no plugin installed

.. during installation I chose sk (Slovak) language in this step : RAILS_ENV=production rake redmine:load_default_data

What can cause the problem? Thanks