Can't install picocontainer

[aslakhellesoy]

bekk-00264a1d1d4c:cuke4duke aslakhellesoy$ jruby --version
jruby 1.4.0 (ruby 1.8.7 patchlevel 174) (2009-11-02 69fbfa3) (Java HotSpot(TM) 64-Bit Server VM 1.6.0_17) [x86_64-java]
bekk-00264a1d1d4c:cuke4duke aslakhellesoy$ maven_gem install org.picocontainer picocontainer 2.10.2
/Users/aslakhellesoy/.rvm/rubies/jruby-1.4.0/lib/ruby/1.8/fileutils.rb:1388:in `fu_list': undefined method `to_str' for nil:NilClass (NoMethodError)
    from /Users/aslakhellesoy/.rvm/rubies/jruby-1.4.0/lib/ruby/1.8/fileutils.rb:1388:in `each'
    from /Users/aslakhellesoy/.rvm/rubies/jruby-1.4.0/lib/ruby/1.8/fileutils.rb:1388:in `map'
    from /Users/aslakhellesoy/.rvm/rubies/jruby-1.4.0/lib/ruby/1.8/fileutils.rb:1388:in `fu_list'
    from /Users/aslakhellesoy/.rvm/rubies/jruby-1.4.0/lib/ruby/1.8/fileutils.rb:544:in `rm'
    from /Users/aslakhellesoy/.rvm/rubies/jruby-1.4.0/lib/ruby/1.8/fileutils.rb:571:in `rm_f'
    from /Users/aslakhellesoy/.rvm/gems/jruby-1.4.0/gems/maven_gem-0.0.2/lib/mvn_gem.rb:21:in `install'
    from /Users/aslakhellesoy/.rvm/gems/jruby-1.4.0/gems/maven_gem-0.0.2/lib/mvn_gem.rb:28
    from /Users/aslakhellesoy/.rvm/gems/jruby-1.4.0/gems/maven_gem-0.0.2/lib/mvn_gem.rb:31:in `require'
    from /Users/aslakhellesoy/.rvm/rubies/jruby-1.4.0/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:31:in `require'
    from /Users/aslakhellesoy/.rvm/gems/jruby-1.4.0/gems/maven_gem-0.0.2/bin/maven_gem:3
    from /Users/aslakhellesoy/.rvm/gems/jruby-1.4.0/gems/maven_gem-0.0.2/bin/maven_gem:19:in `load'
    from /Users/aslakhellesoy/.rvm/gems/jruby-1.4.0/bin/maven_gem:19