JRuby on Rails rake db: tasks all abort with jdbc mysql
$ rake db:create --trace
    rake aborted!
    undefined method `each' for nil:NilClass
    /Users/rath_rio/.rvm/gems/jruby-1.6.6@webgrouper/gems/activerecord-jdbc-adapter-1.2.2/lib/arjdbc/jdbc/jdbc.rake:15:in `redefine_task'
    /Users/rath_rio/.rvm/gems/jruby-1.6.6@webgrouper/gems/activerecord-jdbc-adapter-1.2.2/lib/arjdbc/jdbc/jdbc.rake:23:in `(root)'
    /Users/rath_rio/.rvm/gems/jruby-1.6.6@webgrouper/gems/rake-0.9.2.2/lib/rake/task_manager.rb:207:in `in_namespace'
    /Users/rath_rio/.rvm/gems/jruby-1.6.6@webgrouper/gems/rake-0.9.2.2/lib/rake/dsl_definition.rb:102:in `namespace'
    /Users/rath_rio/.rvm/gems/jruby-1.6.6@webgrouper/gems/activerecord-jdbc-adapter-1.2.2/lib/arjdbc/jdbc/jdbc.rake:22:in `(root)'
    org/jruby/RubyKernel.java:1052:in `load'
    /Users/rath_rio/.rvm/gems/jruby-1.6.6@webgrouper/gems/activerecord-jdbc-adapter-1.2.2/lib/arjdbc/jdbc/jdbc.rake:234:in `load'
    /Users/rath_rio/.rvm/gems/jruby-1.6.6@webgrouper/gems/activesupport-3.1.0/lib/active_support/dependencies.rb:223:in `load_dependency'
    /Users/rath_rio/.rvm/gems/jruby-1.6.6@webgrouper/gems/activesupport-3.1.0/lib/active_support/dependencies.rb:640:in `new_constants_in'
    /Users/rath_rio/.rvm/gems/jruby-1.6.6@webgrouper/gems/activesupport-3.1.0/lib/active_support/dependencies.rb:639:in `new_constants_in'
    /Users/rath_rio/.rvm/gems/jruby-1.6.6@webgrouper/gems/activesupport-3.1.0/lib/active_support/dependencies.rb:223:in `load_dependency'
    /Users/rath_rio/.rvm/gems/jruby-1.6.6@webgrouper/gems/activesupport-3.1.0/lib/active_support/dependencies.rb:234:in `load'
    /Users/rath_rio/.rvm/gems/jruby-1.6.6@webgrouper/gems/rake-0.9.2.2/lib/rake/rake_module.rb:25:in `load_rakefile'
    /Users/rath_rio/.rvm/gems/jruby-1.6.6@webgrouper/gems/rake-0.9.2.2/lib/rake/default_loader.rb:6:in `load'
    /Users/rath_rio/.rvm/gems/jruby-1.6.6@webgrouper/gems/rake-0.9.2.2/lib/rake/application.rb:569:in `load_imports'
    /Users/rath_rio/.rvm/gems/jruby-1.6.6@webgrouper/gems/rake-0.9.2.2/lib/rake/application.rb:508:in `raw_load_rakefile'
    /Users/rath_rio/.rvm/gems/jruby-1.6.6@webgrouper/gems/rake-0.9.2.2/lib/rake/application.rb:82:in `load_rakefile'
    /Users/rath_rio/.rvm/gems/jruby-1.6.6@webgrouper/gems/rake-0.9.2.2/lib/rake/application.rb:133:in `standard_exception_handling'
    /Users/rath_rio/.rvm/gems/jruby-1.6.6@webgrouper/gems/rake-0.9.2.2/lib/rake/application.rb:81:in `load_rakefile'
    /Users/rath_rio/.rvm/gems/jruby-1.6.6@webgrouper/gems/rake-0.9.2.2/lib/rake/application.rb:65:in `run'
    /Users/rath_rio/.rvm/gems/jruby-1.6.6@webgrouper/gems/rake-0.9.2.2/lib/rake/application.rb:133:in `standard_exception_handling'
    /Users/rath_rio/.rvm/gems/jruby-1.6.6@webgrouper/gems/rake-0.9.2.2/lib/rake/application.rb:63:in `run'
    /Users/rath_rio/.rvm/gems/jruby-1.6.6@webgrouper/gems/rake-0.9.2.2/bin/rake:33:in `(root)'
    org/jruby/RubyKernel.java:1052:in `load'
    /Users/rath_rio/.rvm/gems/jruby-1.6.6@webgrouper/bin/rake:19:in `(root)'

our system specification:
Java SE 6
JRuby 1.6.6
Rails 3.1

we use following gems for our datebase:
gem 'mysql2', '~>0.3.0'
gem "jdbc-mysql", "~> 5.1.13"
gem "activerecord-jdbc-adapter", "~> 1.2.2"
gem "activerecord-jdbcmysql-adapter", "~> 1.2.2"

our database.yml file:
development:
    database: webgrouper_development
    adapter: jdbcmysql
    encoding: utf8
    reconnect: true
    pool: 5
    username: root
    password:
    host: 127.0.0.1

test:
    database: webgrouper_test
    adapter: jdbcmysql
    encoding: utf8
    reconnect: false
    pool: 5
    username: root
    password:
    host: 127.0.0.1

production:
    database: webgrouper_production
    adapter: jdbcmysql
    encoding: utf8
    reconnect: false
    pool: 5
    username: root
    password:
    host: 127.0.0.1