[root@helios 3]# middleman server
/usr/local/lib/ruby/gems/1.9.1/gems/bundler-1.3.5/lib/bundler/runtime.rb:33:in `block in setup': You have already activated listen 1.3.1, but your Gemfile requires listen 0.7.3. Using bundle exec may solve this. (Gem::LoadError)
        from /usr/local/lib/ruby/gems/1.9.1/gems/bundler-1.3.5/lib/bundler/runtime.rb:19:in `setup'
        from /usr/local/lib/ruby/gems/1.9.1/gems/bundler-1.3.5/lib/bundler.rb:120:in `setup'
        from /usr/local/lib/ruby/gems/1.9.1/gems/bundler-1.3.5/lib/bundler/setup.rb:7:in `<top (required)>'
        from /usr/local/lib/ruby/1.9.1/rubygems/custom_require.rb:55:in `require'
        from /usr/local/lib/ruby/1.9.1/rubygems/custom_require.rb:55:in `require'
        from /usr/local/lib/ruby/gems/1.9.1/gems/middleman-core-3.2.0/lib/middleman-core/load_paths.rb:30:in `setup_load_paths'
        from /usr/local/lib/ruby/gems/1.9.1/gems/middleman-core-3.2.0/bin/middleman:10:in `<top (required)>'
        from /usr/local/bin/middleman:23:in `load'
        from /usr/local/bin/middleman:23:in `<main>'