Ruby on Rails: RubyGem version error: rack(1.0.0 not ~> 1.0.1) (RuntimeError)

/Library/Ruby/Gems/1.8/gems/rails-2.3.5/lib/initializer.rb:271:in `require_frameworks': RubyGem version error: rack(1.0.0 not ~> 1.0.1) (RuntimeError)
	from /Library/Ruby/Gems/1.8/gems/rails-2.3.5/lib/initializer.rb:134:in `process'
	from /Library/Ruby/Gems/1.8/gems/rails-2.3.5/lib/initializer.rb:113:in `send'
	from /Library/Ruby/Gems/1.8/gems/rails-2.3.5/lib/initializer.rb:113:in `run'
	from /Volumes/Data/study/ruby/blog/config/environment.rb:9
	from /Library/Ruby/Site/1.8/rubygems/custom_require.rb:31:in `gem_original_require'
	from /Library/Ruby/Site/1.8/rubygems/custom_require.rb:31:in `require'
	from /Library/Ruby/Gems/1.8/gems/rails-2.3.5/lib/commands/generate.rb:1
	from /Library/Ruby/Site/1.8/rubygems/custom_require.rb:31:in `gem_original_require'
	from /Library/Ruby/Site/1.8/rubygems/custom_require.rb:31:in `require'
	from ./script/generate:3

$ sudo gem uninstall rack

Select gem to uninstall:
 1. rack-1.0.0
 2. rack-1.1.0
 3. All versions
> 1

You have requested to uninstall the gem:
	rack-1.0.0
actionpack-2.3.5 depends on [rack (~> 1.0.0)]
actionpack-2.3.4 depends on [rack (~> 1.0.0)]
If you remove this gems, one or more dependencies will not be met.
Continue with Uninstall? [Yn]  y
Successfully uninstalled rack-1.0.0

sudo gem install -v=2.3.5 rails

Successfully installed rack-1.0.1
1 gem installed
Installing ri documentation for rack-1.0.1...
Installing RDoc documentation for rack-1.0.1...