Redmine

So far, the problem only happens when running with "RAILS_ENV=development".
I get the following stack while deleting a priority still assigned to at least one issue:

TypeError (can't dump anonymous class Class):
/opt/ruby-enterprise-1.8.7/lib/ruby/1.8/yaml/rubytypes.rb:6:in `to_yaml'
/opt/redmine-0.9.3/vendor/rails/activerecord/lib/active_record/connection_adapters/abstract/quoting.rb:31:in `quote'
/opt/redmine-0.9.3/vendor/rails/activerecord/lib/active_record/connection_adapters/mysql_adapter.rb:236:in `quote'
/opt/redmine-0.9.3/vendor/rails/activerecord/lib/active_record/base.rb:2392:in `quote_bound_value'
/opt/redmine-0.9.3/vendor/rails/activerecord/lib/active_record/base.rb:2352:in `replace_bind_variables'
/opt/redmine-0.9.3/vendor/rails/activerecord/lib/active_record/base.rb:2352:in `gsub'
/opt/redmine-0.9.3/vendor/rails/activerecord/lib/active_record/base.rb:2352:in `replace_bind_variables'
/opt/redmine-0.9.3/vendor/rails/activerecord/lib/active_record/base.rb:2341:in `sanitize_sql_array'
/opt/redmine-0.9.3/vendor/rails/activerecord/lib/active_record/base.rb:2230:in `sanitize_sql'
/opt/redmine-0.9.3/vendor/rails/activerecord/lib/active_record/base.rb:1494:in `merge_conditions'
/opt/redmine-0.9.3/vendor/rails/activerecord/lib/active_record/base.rb:1492:in `each'
/opt/redmine-0.9.3/vendor/rails/activerecord/lib/active_record/base.rb:1492:in `merge_conditions'
/opt/redmine-0.9.3/vendor/rails/activerecord/lib/active_record/base.rb:1804:in `add_conditions!'
/opt/redmine-0.9.3/vendor/rails/activerecord/lib/active_record/base.rb:1687:in `construct_finder_sql'
/opt/redmine-0.9.3/vendor/rails/activerecord/lib/active_record/base.rb:1548:in `find_every'
/opt/redmine-0.9.3/vendor/rails/activerecord/lib/active_record/base.rb:615:in `find'
/opt/redmine-0.9.3/app/controllers/enumerations_controller.rb:84:in `destroy'