error msg for Middleman init

WARN: Unresolved specs during Gem::Specification.reset:
      rack (>= 1.4.5)
      rack-test (~> 0.6.1)
      thor (< 2.0, >= 0.15.2)
      activesupport (~> 3.2.6)
      ffi (>= 0.5.0)
      i18n (~> 0.6.1)
WARN: Clearing out unresolved specs.
Please report a bug if this causes problems.
e:/ruby193/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 1.2.3, but your Gemfile requi
res listen 0.5.2. Using bundle exec may solve this. (Gem::LoadError)
        from e:/ruby193/lib/ruby/gems/1.9.1/gems/bundler-1.3.5/lib/bundler/runti
me.rb:19:in `setup'
        from e:/ruby193/lib/ruby/gems/1.9.1/gems/bundler-1.3.5/lib/bundler.rb:12
0:in `setup'
        from e:/ruby193/lib/ruby/gems/1.9.1/gems/bundler-1.3.5/lib/bundler/setup
.rb:7:in `<top (required)>'
        from e:/ruby193/lib/ruby/site_ruby/1.9.1/rubygems/core_ext/kernel_requir
e.rb:106:in `require'
        from e:/ruby193/lib/ruby/site_ruby/1.9.1/rubygems/core_ext/kernel_requir
e.rb:106:in `require'
        from e:/ruby193/lib/ruby/gems/1.9.1/gems/middleman-core-3.1.5/lib/middle
man-core/load_paths.rb:30:in `setup_load_paths'
        from e:/ruby193/lib/ruby/gems/1.9.1/gems/middleman-core-3.1.5/bin/middle
man:10:in `<top (required)>'
        from e:/Ruby193/bin/middleman:23:in `load'
        from e:/Ruby193/bin/middleman:23:in `<main>'