The driver encountered an error: java.lang.NullPointerException: null

C:/Programme/NetBeans 6.1 Beta/ruby2/jruby-1.1RC1/lib/ruby/gems/1.8/gems/activerecord-jdbc-adapter-0.7/lib/active_record/connection_adapters/jdbc_adapter.rb:298:in `initialize'
C:/Programme/NetBeans 6.1 Beta/ruby2/jruby-1.1RC1/lib/ruby/gems/1.8/gems/activerecord-jdbc-adapter-0.7/lib/active_record/connection_adapters/jdbc_adapter.rb:41:in `new'
C:/Programme/NetBeans 6.1 Beta/ruby2/jruby-1.1RC1/lib/ruby/gems/1.8/gems/activerecord-jdbc-adapter-0.7/lib/active_record/connection_adapters/jdbc_adapter.rb:41:in `jdbc_connection'
C:/Programme/NetBeans 6.1 Beta/ruby2/jruby-1.1RC1/lib/ruby/gems/1.8/gems/activerecord-2.0.2/lib/active_record/connection_adapters/abstract/connection_specification.rb:291:in `connection='
C:/Programme/NetBeans 6.1 Beta/ruby2/jruby-1.1RC1/lib/ruby/gems/1.8/gems/activerecord-2.0.2/lib/active_record/connection_adapters/abstract/connection_specification.rb:259:in `retrieve_connection'
C:/Programme/NetBeans 6.1 Beta/ruby2/jruby-1.1RC1/lib/ruby/gems/1.8/gems/activerecord-2.0.2/lib/active_record/connection_adapters/abstract/connection_specification.rb:78:in `connection'
C:/Programme/NetBeans 6.1 Beta/ruby2/jruby-1.1RC1/lib/ruby/gems/1.8/gems/activerecord-2.0.2/lib/active_record/query_cache.rb:8:in `cache'
C:/Programme/NetBeans 6.1 Beta/ruby2/jruby-1.1RC1/lib/ruby/gems/1.8/gems/actionpack-2.0.2/lib/action_controller/caching.rb:677:in `perform_action_with_caching'
C:/Programme/NetBeans 6.1 Beta/ruby2/jruby-1.1RC1/lib/ruby/gems/1.8/gems/actionpack-2.0.2/lib/action_controller/caching.rb:677:in `process'
C:/Programme/NetBeans 6.1 Beta/ruby2/jruby-1.1RC1/lib/ruby/gems/1.8/gems/actionpack-2.0.2/lib/action_controller/filters.rb:685:in `process_with_filters'
C:/Programme/NetBeans 6.1 Beta/ruby2/jruby-1.1RC1/lib/ruby/gems/1.8/gems/actionpack-2.0.2/lib/action_controller/session_management.rb:123:in `process_with_session_management_support'
C:/Programme/NetBeans 6.1 Beta/ruby2/jruby-1.1RC1/lib/ruby/gems/1.8/gems/actionpack-2.0.2/lib/action_controller/base.rb:388:in `process'
C:/Programme/NetBeans 6.1 Beta/ruby2/jruby-1.1RC1/lib/ruby/gems/1.8/gems/actionpack-2.0.2/lib/action_controller/dispatcher.rb:171:in `handle_request'
C:/Programme/NetBeans 6.1 Beta/ruby2/jruby-1.1RC1/lib/ruby/gems/1.8/gems/actionpack-2.0.2/lib/action_controller/dispatcher.rb:115:in `dispatch'
C:/Programme/NetBeans 6.1 Beta/ruby2/jruby-1.1RC1/lib/ruby/gems/1.8/gems/actionpack-2.0.2/lib/action_controller/dispatcher.rb:126:in `dispatch_cgi'
C:/Programme/NetBeans 6.1 Beta/ruby2/jruby-1.1RC1/lib/ruby/gems/1.8/gems/actionpack-2.0.2/lib/action_controller/dispatcher.rb:9:in `dispatch'
C:/Programme/NetBeans 6.1 Beta/ruby2/jruby-1.1RC1/lib/ruby/gems/1.8/gems/rails-2.0.2/lib/webrick_server.rb:112:in `handle_dispatch'
C:/Programme/NetBeans 6.1 Beta/ruby2/jruby-1.1RC1/lib/ruby/gems/1.8/gems/rails-2.0.2/lib/webrick_server.rb:78:in `service'
C:/Programme/NetBeans 6.1 Beta/ruby2/jruby-1.1RC1/lib/ruby/1.8/webrick/httpserver.rb:104:in `service'
C:/Programme/NetBeans 6.1 Beta/ruby2/jruby-1.1RC1/lib/ruby/1.8/webrick/httpserver.rb:65:in `run'
C:/Programme/NetBeans 6.1 Beta/ruby2/jruby-1.1RC1/lib/ruby/1.8/webrick/server.rb:173:in `start_thread'
C:/Programme/NetBeans 6.1 Beta/ruby2/jruby-1.1RC1/lib/ruby/1.8/webrick/server.rb:162:in `start'