How do you debug and fix gem errors like below? Although the below case is very specific, I'm also looking for solution to related problems like "gem already activated [...]", and resources to gem management/debugging.

mycomputer:projectfolder username$ cucumber features
Using the default profile...
WARNING: No DRb server is running. Running features locally:
/Users/username/.gem/ruby/1.8/gems/rails-2.3.5/lib/rails/gem_dependency.rb:119:Warning: Gem::Dependency#version_requirements is deprecated and will be removed on or after August 2010.  Use #requirement
can't activate , already activated ruby-hmac-0.4.0 (Gem::Exception)
/Users/username/.gem/ruby/1.8/gems/rails-2.3.5/lib/rails/gem_dependency.rb:101:in `specification'
/Users/username/.gem/ruby/1.8/gems/rails-2.3.5/lib/rails/plugin/locator.rb:81:in `plugins'
/Library/Ruby/Site/1.8/rubygems/custom_require.rb:31:in `inject'
/Users/username/.gem/ruby/1.8/gems/rails-2.3.5/lib/rails/plugin/locator.rb:81:in `each'
/Users/username/.gem/ruby/1.8/gems/rails-2.3.5/lib/rails/plugin/locator.rb:81:in `inject'
/Users/username/.gem/ruby/1.8/gems/rails-2.3.5/lib/rails/plugin/locator.rb:81:in `plugins'
/Users/username/.gem/ruby/1.8/gems/rails-2.3.5/lib/rails/plugin/loader.rb:109:in `locate_plugins'
/Users/username/.gem/ruby/1.8/gems/rails-2.3.5/lib/rails/plugin/loader.rb:108:in `map'
/Users/username/.gem/ruby/1.8/gems/rails-2.3.5/lib/rails/plugin/loader.rb:108:in `locate_plugins'
/Users/username/.gem/ruby/1.8/gems/rails-2.3.5/lib/rails/plugin/loader.rb:32:in `all_plugins'
/Users/username/.gem/ruby/1.8/gems/rails-2.3.5/lib/rails/plugin/loader.rb:22:in `plugins'
/Users/username/.gem/ruby/1.8/gems/rails-2.3.5/lib/rails/plugin/loader.rb:53:in `add_plugin_load_paths'
/Users/username/.gem/ruby/1.8/gems/rails-2.3.5/lib/initializer.rb:294:in `add_plugin_load_paths'
/Users/username/.gem/ruby/1.8/gems/rails-2.3.5/lib/initializer.rb:136:in `process'
/Users/username/.gem/ruby/1.8/gems/rails-2.3.5/lib/initializer.rb:113:in `send'
/Users/username/.gem/ruby/1.8/gems/rails-2.3.5/lib/initializer.rb:113:in `run'
/Users/username/Documents/projectfolder.0/sites/projectfolder/config/environment.rb:9
/Library/Ruby/Site/1.8/rubygems/custom_require.rb:31:in `gem_original_require'
/Library/Ruby/Site/1.8/rubygems/custom_require.rb:31:in `polyglot_original_require'
/Library/Ruby/Gems/1.8/gems/polyglot-0.2.9/lib/polyglot.rb:70:in `require'
./features/support/env.rb:12
/Library/Ruby/Gems/1.8/gems/spork-0.7.5/lib/spork.rb:23:in `prefork'
./features/support/env.rb:9
/Library/Ruby/Site/1.8/rubygems/custom_require.rb:31:in `gem_original_require'
/Library/Ruby/Site/1.8/rubygems/custom_require.rb:31:in `polyglot_original_require'
/Library/Ruby/Gems/1.8/gems/polyglot-0.2.9/lib/polyglot.rb:70:in `require'
/Library/Ruby/Gems/1.8/gems/cucumber-0.4.4/bin/../lib/cucumber/rb_support/rb_language.rb:124:in `load_code_file'
/Library/Ruby/Gems/1.8/gems/cucumber-0.4.4/bin/../lib/cucumber/step_mother.rb:84:in `load_code_file'
/Library/Ruby/Gems/1.8/gems/cucumber-0.4.4/bin/../lib/cucumber/step_mother.rb:76:in `load_code_files'
/Library/Ruby/Gems/1.8/gems/cucumber-0.4.4/bin/../lib/cucumber/step_mother.rb:75:in `each'
/Library/Ruby/Gems/1.8/gems/cucumber-0.4.4/bin/../lib/cucumber/step_mother.rb:75:in `load_code_files'
/Library/Ruby/Gems/1.8/gems/cucumber-0.4.4/bin/../lib/cucumber/cli/main.rb:47:in `execute!'
/Library/Ruby/Gems/1.8/gems/cucumber-0.4.4/bin/../lib/cucumber/cli/main.rb:24:in `execute'
/Library/Ruby/Gems/1.8/gems/cucumber-0.4.4/bin/cucumber:8
/usr/bin/cucumber:19:in `load'
/usr/bin/cucumber:19

And this is the output from gem list

actionmailer (2.3.5, 2.2.2, 1.3.6)
actionpack (2.3.5, 2.2.2, 1.13.6)
actionwebservice (1.2.6)
activerecord (2.3.5, 2.2.2, 1.15.6)
activeresource (2.3.5, 2.2.2)
activesupport (2.3.5, 2.2.2, 1.4.4)
acts_as_ferret (0.4.4, 0.4.3)
adamwiggins-rest-client (1.0.4)
aslakhellesoy-webrat (0.4.4.1)
aslakjo-comatose (2.0.5.12)
authlogic (2.1.3)
authlogic-oid (1.0.4)
builder (2.1.2)
capistrano (2.5.17, 2.5.2)
cgi_multipart_eof_fix (2.5.0)
configuration (1.1.0)
cucumber (0.4.4)
cucumber-rails (0.3.0)
daemons (1.0.10)
database_cleaner (0.5.0)
diff-lcs (1.1.2)
dnssd (1.3.1, 0.6.0)
fakeweb (1.2.8)
fastthread (1.0.7, 1.0.1)
fcgi (0.8.8, 0.8.7)
ferret (0.11.6)
gem_plugin (0.2.3)
gemcutter (0.4.1)
heroku (1.8.0)
highline (1.5.2, 1.5.0)
hoe (2.5.0)
hpricot (0.8.2, 0.6.164)
json (1.2.2)
json_pure (1.2.2)
launchy (0.3.5)
libxml-ruby (1.1.3, 1.1.2)
linecache (0.43)
log4r (1.1.5)
mime-types (1.16)
mongrel (1.1.5)
mysql (2.8.1)
needle (1.3.0)
net-scp (1.0.2, 1.0.1)
net-sftp (2.0.4, 2.0.1, 1.1.1)
net-ssh (2.0.20, 2.0.4, 1.1.4)
net-ssh-gateway (1.0.1, 1.0.0)
nifty-generators (0.3.2)
nokogiri (1.4.1)
oauth (0.3.6)
oniguruma (1.1.0)
plist (3.1.0)
polyglot (0.2.9)
rack (1.1.0, 1.0.1)
rack-test (0.5.3)
rails (2.3.5, 2.2.2, 1.2.6)
rake (0.8.7, 0.8.3)
RedCloth (4.2.2, 4.1.1)
rest-client (1.4.0)
rspec (1.3.0)
rspec-rails (1.3.2)
ruby-activeldap (0.8.3.1)
ruby-debug-base (0.10.3)
ruby-debug-ide (0.4.9)
ruby-hmac (0.4.0)
ruby-net-ldap (0.0.4)
ruby-openid (2.1.7, 2.1.2)
ruby-yadis (0.3.4)
rubyforge (2.0.4)
rubygems-update (1.3.6)
rubynode (0.1.5)
rubyzip (0.9.4)
sanitize (1.2.0)
sequel (3.0.0)
sinatra (0.9.2)
spork (0.7.5)
sqlite3-ruby (1.2.5, 1.2.4)
taps (0.2.26)
term-ansicolor (1.0.4)
termios (0.9.4)
textpow (0.10.1)
thor (0.9.9)
treetop (1.4.2)
twitter4r (0.3.2, 0.3.1)
ultraviolet (0.10.2)
webrat (0.7.0)
will_paginate (2.3.12)
xmpp4r (0.5, 0.4)