Why won't Rails' console start or make new apps? - ruby-on-rails

Question

A few days ago I updated my gems because things weren't running so fine, so I went back to 1.4.2. Since then I'm getting all kind of weird errors.
I'm using Ruby 2.0.0p247, Rails 4.0 and Ubuntu.
If I try to start a new app using rails new eraseme, everything goes fine until it's time to do bundle install. The output is:
run bundle install
/usr/local/lib/ruby/gems/2.0.0/gems/railties-4.0.0/lib/rails/generators/app_base.rb:270:in `require': cannot load such file -- bundler (LoadError)
from /usr/local/lib/ruby/gems/2.0.0/gems/railties-4.0.0/lib/rails/generators/app_base.rb:270:in `bundle_command'
from /usr/local/lib/ruby/gems/2.0.0/gems/railties-4.0.0/lib/rails/generators/app_base.rb:277:in `run_bundle'
from (eval):1:in `run_bundle'
from /usr/local/lib/ruby/gems/2.0.0/gems/thor-0.18.1/lib/thor/command.rb:27:in `run'
from /usr/local/lib/ruby/gems/2.0.0/gems/thor-0.18.1/lib/thor/invocation.rb:120:in `invoke_command'
from /usr/local/lib/ruby/gems/2.0.0/gems/thor-0.18.1/lib/thor/invocation.rb:127:in `block in invoke_all'
from /usr/local/lib/ruby/gems/2.0.0/gems/thor-0.18.1/lib/thor/invocation.rb:127:in `each'
from /usr/local/lib/ruby/gems/2.0.0/gems/thor-0.18.1/lib/thor/invocation.rb:127:in `map'
from /usr/local/lib/ruby/gems/2.0.0/gems/thor-0.18.1/lib/thor/invocation.rb:127:in `invoke_all'
from /usr/local/lib/ruby/gems/2.0.0/gems/thor-0.18.1/lib/thor/group.rb:233:in `dispatch'
from /usr/local/lib/ruby/gems/2.0.0/gems/thor-0.18.1/lib/thor/base.rb:439:in `start'
from /usr/local/lib/ruby/gems/2.0.0/gems/railties-4.0.0/lib/rails/commands/application.rb:43:in `<top (required)>'
from /usr/local/lib/ruby/gems/2.0.0/gems/railties-4.0.0/lib/rails/cli.rb:15:in `require'
from /usr/local/lib/ruby/gems/2.0.0/gems/railties-4.0.0/lib/rails/cli.rb:15:in `<top (required)>'
from /usr/local/lib/ruby/gems/2.0.0/gems/railties-4.0.0/bin/rails:9:in `require'
from /usr/local/lib/ruby/gems/2.0.0/gems/railties-4.0.0/bin/rails:9:in `<top (required)>'
from /usr/local/bin/rails:23:in `load'
from /usr/local/bin/rails:23:in `<main>'
If I try to open the console, I get:
>> bundle exec rails console
Loading development environment (Rails 4.0.0)
/usr/local/lib/ruby/2.0.0/irb/locale.rb:150:in `block in search_file': undefined method `try_activate' for Gem:Module (NoMethodError)
from /usr/local/lib/ruby/2.0.0/irb/locale.rb:158:in `block in each_localized_path'
from /usr/local/lib/ruby/2.0.0/irb/locale.rb:167:in `each_sublocale'
from /usr/local/lib/ruby/2.0.0/irb/locale.rb:157:in `each_localized_path'
from /usr/local/lib/ruby/2.0.0/irb/locale.rb:145:in `search_file'
from /usr/local/lib/ruby/2.0.0/irb/locale.rb:124:in `find'
from /usr/local/lib/ruby/2.0.0/irb/locale.rb:108:in `load'
from /usr/local/lib/ruby/2.0.0/irb/locale.rb:32:in `initialize'
from /usr/local/lib/ruby/2.0.0/irb/init.rb:114:in `new'
from /usr/local/lib/ruby/2.0.0/irb/init.rb:114:in `init_config'
from /usr/local/lib/ruby/2.0.0/irb/init.rb:16:in `setup'
from /usr/local/lib/ruby/2.0.0/irb.rb:380:in `start'
from /usr/local/lib/ruby/gems/2.0.0/gems/railties-4.0.0/lib/rails/commands/console.rb:90:in `start'
from /usr/local/lib/ruby/gems/2.0.0/gems/railties-4.0.0/lib/rails/commands/console.rb:9:in `start'
from /usr/local/lib/ruby/gems/2.0.0/gems/railties-4.0.0/lib/rails/commands.rb:64:in `<top (required)>'
from bin/rails:4:in `require'
from bin/rails:4:in `<main>'

Answer 1

Have you already installed bundler? If not, try:
gem install bundler
If so, try:
gem install bundler --pre

Answer 2

If you running Ruby version manager, what version are you running? You might be set to the wrong version of Ruby.
I think it would be easier for you if you used RVM or some other version manager.

Answer 3

if you have multiple versions of rubygems installed, uninstall all but the one you want to use.
I think rails 4 requires rubygems 2.x.
Also check the bundler version.