vagrant up で謎のエラー

$ vagrant up
Bringing machine 'default' up with 'virtualbox' provider...
==> default: Checking if box 'bento/centos-6.8' version '2.3.4' is up to date...
Your VM has become "inaccessible." Unfortunately, this is a critical error
with VirtualBox that Vagrant can not cleanly recover from. Please open VirtualBox
and clear out your inaccessible virtual machines or find a way to fix
them.

さっきまで起動できていた仮想サーバが放置していたら接続が切れた上に繋がらなくなりました

調べたところファイル名を変えたり削除してみたりしたのですが無理でした

お願いいたします

＜以下追記＞
対象のVMとやらがわからずいろいろいじったらエラーが変わりました。

$ vagrant up
Traceback (most recent call last):
	2: from /opt/vagrant/embedded/gems/2.2.9/gems/vagrant-2.2.9/bin/vagrant:87:in `<main>'
	1: from /opt/vagrant/embedded/lib/ruby/2.6.0/rubygems/core_ext/kernel_require.rb:54:in `require'
/opt/vagrant/embedded/lib/ruby/2.6.0/rubygems/core_ext/kernel_require.rb:54:in `require': cannot load such file -- log4r (LoadError)
	13: from /opt/vagrant/embedded/gems/2.2.9/gems/vagrant-2.2.9/bin/vagrant:87:in `<main>'
	12: from /opt/vagrant/embedded/lib/ruby/2.6.0/rubygems/core_ext/kernel_require.rb:34:in `require'
	11: from /opt/vagrant/embedded/lib/ruby/2.6.0/rubygems/core_ext/kernel_require.rb:123:in `rescue in require'
	10: from /opt/vagrant/embedded/lib/ruby/2.6.0/rubygems.rb:212:in `try_activate'
	 9: from /opt/vagrant/embedded/lib/ruby/2.6.0/rubygems/specification.rb:1041:in `find_by_path'
	 8: from /opt/vagrant/embedded/lib/ruby/2.6.0/rubygems/specification.rb:1041:in `find'
	 7: from /opt/vagrant/embedded/lib/ruby/2.6.0/rubygems/specification.rb:1041:in `each'
	 6: from /opt/vagrant/embedded/lib/ruby/2.6.0/rubygems/specification.rb:1042:in `block in find_by_path'
	 5: from /opt/vagrant/embedded/lib/ruby/2.6.0/rubygems/bundler_version_finder.rb:39:in `compatible?'
	 4: from /opt/vagrant/embedded/lib/ruby/2.6.0/rubygems/bundler_version_finder.rb:7:in `bundler_version'
	 3: from /opt/vagrant/embedded/lib/ruby/2.6.0/rubygems/bundler_version_finder.rb:22:in `bundler_version_with_reason'
	 2: from /opt/vagrant/embedded/lib/ruby/2.6.0/rubygems/bundler_version_finder.rb:68:in `lockfile_version'
	 1: from /opt/vagrant/embedded/lib/ruby/2.6.0/rubygems/bundler_version_finder.rb:80:in `lockfile_contents'
/opt/vagrant/embedded/lib/ruby/2.6.0/rubygems/bundler_version_finder.rb:80:in `pwd': Operation not permitted - getcwd (Errno::EPERM)