From the discussion: "vagrant box add fails with cygwin on windows" https://groups.google.com/forum/#!searchin/vagrant-up/cygwin/vagrant-up/vah9aGxCKbc/5ZE3_dx5Kg4J Output from running vagrant and attempting to add box under Cygwin.

gistfile1.txt

$ vagrant box add precise32 http://files.vagrantup.com/precise32.box
Downloading with Vagrant::Downloaders::HTTP...
Downloading box: http://files.vagrantup.com/precise32.box
Extracting box...5113792 / 295255040)
Cleaning up downloaded box...
C:/vagrant/vagrant/embedded/gems/gems/vagrant-1.1.2/lib/vagrant/util/subprocess.rb:81:in `rescue in execute': The system cannot find the file specified. (2) (Vagrant::Util::Subprocess::LaunchError)
        from C:/vagrant/vagrant/embedded/gems/gems/vagrant-1.1.2/lib/vagrant/util/subprocess.rb:74:in `execute'
        from C:/vagrant/vagrant/embedded/gems/gems/vagrant-1.1.2/lib/vagrant/util/subprocess.rb:20:in `execute'
        from C:/vagrant/vagrant/embedded/gems/gems/vagrant-1.1.2/lib/vagrant/box_collection.rb:104:in `block in add'
        from C:/vagrant/vagrant/embedded/lib/ruby/1.9.1/tmpdir.rb:83:in `mktmpdir'
        from C:/vagrant/vagrant/embedded/gems/gems/vagrant-1.1.2/lib/vagrant/box_collection.rb:99:in `add'
        from C:/vagrant/vagrant/embedded/gems/gems/vagrant-1.1.2/lib/vagrant/action/builtin/box_add.rb:35:in `call'
        from C:/vagrant/vagrant/embedded/gems/gems/vagrant-1.1.2/lib/vagrant/action/warden.rb:34:in `call'
        from C:/vagrant/vagrant/embedded/gems/gems/vagrant-1.1.2/lib/vagrant/action/builder.rb:109:in `call'
        from C:/vagrant/vagrant/embedded/gems/gems/vagrant-1.1.2/lib/vagrant/action/runner.rb:61:in `block in run'
        from C:/vagrant/vagrant/embedded/gems/gems/vagrant-1.1.2/lib/vagrant/util/busy.rb:19:in `busy'
        from C:/vagrant/vagrant/embedded/gems/gems/vagrant-1.1.2/lib/vagrant/action/runner.rb:61:in `run'
        from C:/vagrant/vagrant/embedded/gems/gems/vagrant-1.1.2/plugins/commands/box/command/add.rb:33:in `execute'
        from C:/vagrant/vagrant/embedded/gems/gems/vagrant-1.1.2/plugins/commands/box/command/root.rb:47:in `execute'
        from C:/vagrant/vagrant/embedded/gems/gems/vagrant-1.1.2/lib/vagrant/cli.rb:46:in `execute'
        from C:/vagrant/vagrant/embedded/gems/gems/vagrant-1.1.2/lib/vagrant/environment.rb:406:in `cli'
        from C:/vagrant/vagrant/embedded/gems/gems/vagrant-1.1.2/bin/vagrant:60:in `<top (required)>'
        from C:/vagrant/vagrant/embedded/gems/bin/vagrant:23:in `load'
        from C:/vagrant/vagrant/embedded/gems/bin/vagrant:23:in `<main>'

having the same issue.