Vagrant error in check_port_collisions

gistfile1.txt

[ass_webserver] Importing base box 'centos-60-x86_64'...
[ass_webserver] Progress: 90%/usr/lib/ruby/gems/1.8/gems/vagrant-0.9.0.dev/lib/vagrant/driver/virtualbox.rb:226: warning: regexp has invalid interval
/usr/lib/ruby/gems/1.8/gems/vagrant-0.9.0.dev/lib/vagrant/driver/virtualbox.rb:226: warning: regexp has `}' without escape
[ass_webserver] The guest additions on this VM do not match the install version of
VirtualBox! This may cause things such as forwarded ports, shared
folders, and more to not work properly. If any of those things fail on
this machine, please update the guest additions and repackage the
box.

Guest Additions Version: 4.1.0
VirtualBox Version: 4.1.6
[ass_webserver] Matching MAC address for NAT networking...
[ass_webserver] Clearing any previously set forwarded ports...
Vagrant::Action::Environment
[ass_webserver] Destroying VM and associated drives...
/usr/lib/ruby/gems/1.8/gems/vagrant-0.9.0.dev/lib/vagrant/action/vm/check_port_collisions.rb:64:in `handle_correct': undefined method `[]' for nil:NilClass (NoMethodError)
	from /usr/lib/ruby/gems/1.8/gems/vagrant-0.9.0.dev/lib/vagrant/action/vm/check_port_collisions.rb:64:in `collect'
	from /usr/lib/ruby/gems/1.8/gems/vagrant-0.9.0.dev/lib/vagrant/action/vm/check_port_collisions.rb:64:in `handle_correct'
	from /usr/lib/ruby/gems/1.8/gems/vagrant-0.9.0.dev/lib/vagrant/action/vm/check_port_collisions.rb:34:in `send'
	from /usr/lib/ruby/gems/1.8/gems/vagrant-0.9.0.dev/lib/vagrant/action/vm/check_port_collisions.rb:34:in `call'
	from /usr/lib/ruby/gems/1.8/gems/vagrant-0.9.0.dev/lib/vagrant/action/vm/check_port_collisions.rb:26:in `each'
	from /usr/lib/ruby/gems/1.8/gems/vagrant-0.9.0.dev/lib/vagrant/action/vm/check_port_collisions.rb:26:in `call'
	from /usr/lib/ruby/gems/1.8/gems/vagrant-0.9.0.dev/lib/vagrant/action/warden.rb:33:in `call'
	from /usr/lib/ruby/gems/1.8/gems/vagrant-0.9.0.dev/lib/vagrant/action/env/set.rb:16:in `call'
	from /usr/lib/ruby/gems/1.8/gems/vagrant-0.9.0.dev/lib/vagrant/action/warden.rb:33:in `call'
	from /usr/lib/ruby/gems/1.8/gems/vagrant-0.9.0.dev/lib/vagrant/action/vm/clear_forwarded_ports.rb:13:in `call'
	from /usr/lib/ruby/gems/1.8/gems/vagrant-0.9.0.dev/lib/vagrant/action/warden.rb:33:in `call'
	from /usr/lib/ruby/gems/1.8/gems/vagrant-0.9.0.dev/lib/vagrant/action/vm/clean_machine_folder.rb:17:in `call'
	from /usr/lib/ruby/gems/1.8/gems/vagrant-0.9.0.dev/lib/vagrant/action/warden.rb:33:in `call'
	from /usr/lib/ruby/gems/1.8/gems/vagrant-0.9.0.dev/lib/vagrant/action/vm/check_accessible.rb:18:in `call'
	from /usr/lib/ruby/gems/1.8/gems/vagrant-0.9.0.dev/lib/vagrant/action/warden.rb:33:in `call'
	from /usr/lib/ruby/gems/1.8/gems/vagrant-0.9.0.dev/lib/vagrant/action/general/validate.rb:14:in `call'
	from /usr/lib/ruby/gems/1.8/gems/vagrant-0.9.0.dev/lib/vagrant/action/warden.rb:33:in `call'
	from /usr/lib/ruby/gems/1.8/gems/vagrant-0.9.0.dev/lib/vagrant/action/vm/match_mac_address.rb:16:in `call'
	from /usr/lib/ruby/gems/1.8/gems/vagrant-0.9.0.dev/lib/vagrant/action/warden.rb:33:in `call'
	from /usr/lib/ruby/gems/1.8/gems/vagrant-0.9.0.dev/lib/vagrant/action/vm/check_guest_additions.rb:33:in `call'
	from /usr/lib/ruby/gems/1.8/gems/vagrant-0.9.0.dev/lib/vagrant/action/warden.rb:33:in `call'
	from /usr/lib/ruby/gems/1.8/gems/vagrant-0.9.0.dev/lib/vagrant/action/vm/import.rb:32:in `call'
	from /usr/lib/ruby/gems/1.8/gems/vagrant-0.9.0.dev/lib/vagrant/action/warden.rb:33:in `call'
	from /usr/lib/ruby/gems/1.8/gems/vagrant-0.9.0.dev/lib/vagrant/action/vm/check_box.rb:28:in `call'
	from /usr/lib/ruby/gems/1.8/gems/vagrant-0.9.0.dev/lib/vagrant/action/warden.rb:33:in `call'
	from /usr/lib/ruby/gems/1.8/gems/vagrant-0.9.0.dev/lib/vagrant/action/vm/check_accessible.rb:18:in `call'
	from /usr/lib/ruby/gems/1.8/gems/vagrant-0.9.0.dev/lib/vagrant/action/warden.rb:33:in `call'
	from /usr/lib/ruby/gems/1.8/gems/vagrant-0.9.0.dev/lib/vagrant/action/general/validate.rb:14:in `call'
	from /usr/lib/ruby/gems/1.8/gems/vagrant-0.9.0.dev/lib/vagrant/action/warden.rb:33:in `call'
	from /usr/lib/ruby/gems/1.8/gems/vagrant-0.9.0.dev/lib/vagrant/action/builder.rb:92:in `call'
	from /usr/lib/ruby/gems/1.8/gems/vagrant-0.9.0.dev/lib/vagrant/action/runner.rb:49:in `run'
	from /usr/lib/ruby/gems/1.8/gems/vagrant-0.9.0.dev/lib/vagrant/util/busy.rb:19:in `busy'
	from /usr/lib/ruby/gems/1.8/gems/vagrant-0.9.0.dev/lib/vagrant/action/runner.rb:49:in `run'
	from /usr/lib/ruby/gems/1.8/gems/vagrant-0.9.0.dev/lib/vagrant/vm.rb:181:in `run_action'
	from /usr/lib/ruby/gems/1.8/gems/vagrant-0.9.0.dev/lib/vagrant/vm.rb:132:in `up'
	from /usr/lib/ruby/gems/1.8/gems/vagrant-0.9.0.dev/lib/vagrant/command/up.rb:32:in `execute'
	from /usr/lib/ruby/gems/1.8/gems/vagrant-0.9.0.dev/lib/vagrant/command/base.rb:101:in `with_target_vms'
	from /usr/lib/ruby/gems/1.8/gems/vagrant-0.9.0.dev/lib/vagrant/command/base.rb:96:in `each'
	from /usr/lib/ruby/gems/1.8/gems/vagrant-0.9.0.dev/lib/vagrant/command/base.rb:96:in `with_target_vms'
	from /usr/lib/ruby/gems/1.8/gems/vagrant-0.9.0.dev/lib/vagrant/command/up.rb:25:in `execute'
	from /usr/lib/ruby/gems/1.8/gems/vagrant-0.9.0.dev/lib/vagrant/cli.rb:38:in `execute'
	from /usr/lib/ruby/gems/1.8/gems/vagrant-0.9.0.dev/lib/vagrant/environment.rb:155:in `cli'
	from /usr/lib/ruby/gems/1.8/gems/vagrant-0.9.0.dev/bin/vagrant:40
	from /usr/bin/vagrant:19:in `load'
	from /usr/bin/vagrant:19