Redmine

I get the following error when I hit the "To-Do" link in the top navigation in Redmine:

NoMethodError (undefined method `visible' for #<Class:0xa535f20>):
/lib/ruby-enterprise-1.8.6/lib/ruby/gems/1.8/gems/activerecord-2.1.2/lib/active_record/base.rb:1672:in `method_missing'
/vendor/plugins/stuff_to_do_plugin/app/controllers/stuff_to_do_controller.rb:112:in `get_time_grid'
/lib/ruby-enterprise-1.8.6/lib/ruby/gems/1.8/gems/activesupport-2.1.2/lib/active_support/callbacks.rb:173:in `send'
/lib/ruby-enterprise-1.8.6/lib/ruby/gems/1.8/gems/activesupport-2.1.2/lib/active_support/callbacks.rb:173:in `evaluate_method'
/lib/ruby-enterprise-1.8.6/lib/ruby/gems/1.8/gems/activesupport-2.1.2/lib/active_support/callbacks.rb:161:in `call'
/lib/ruby-enterprise-1.8.6/lib/ruby/gems/1.8/gems/actionpack-2.1.2/lib/action_controller/filters.rb:191:in `call'
/lib/ruby-enterprise-1.8.6/lib/ruby/gems/1.8/gems/actionpack-2.1.2/lib/action_controller/filters.rb:591:in `run_before_filters'

I don't know how to resolve this. Tried reinstalling (incl. migrations), installed new, fresh redmine. I use Phusion Passenger 2.2.5. On Mongrel, Thin, WebBrick I get the same error message. (CentOS 5) Any hints?