Rails rack 1.0 error

I have this error when I try to start script/server:

/opt/ruby1.8/lib/ruby/site_ruby/1.8/rubygems.rb:827:in `report_activate_error': RubyGem version error: rack(1.0.0 not ~> 1.0.1) (Gem::LoadError)
 from /opt/ruby1.8/lib/ruby/site_ruby/1.8/rubygems.rb:261:in `activate'
 from /opt/ruby1.8/lib/ruby/site_ruby/1.8/rubygems.rb:68:in `gem'
 from /opt/ruby1.8/lib/ruby/gems/1.8/gems/actionpack-2.3.5/lib/action_controller.rb:34
 from /opt/ruby1.8/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:31:in `gem_original_require'
 from /opt/ruby1.8/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:31:in `require'
 from /opt/ruby1.8/lib/ruby/gems/1.8/gems/activesupport-2.3.5/lib/active_support/dependencies.rb:156:in `require'
 from /opt/ruby1.8/lib/ruby/gems/1.8/gems/activesupport-2.3.5/lib/active_support/dependencies.rb:521:in `new_constants_in'
 from /opt/ruby1.8/lib/ruby/gems/1.8/gems/activesupport-2.3.5/lib/active_support/dependencies.rb:156:in `require'
 from /opt/ruby1.8/lib/ruby/gems/1.8/gems/rails-2.3.5/lib/commands/server.rb:2
 from /opt/ruby1.8/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:31:in `gem_original_require'
 from /opt/ruby1.8/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:31:in `require'
 from script/server:3

It's very annoying because, I did:

Successfully installed rack-1.1.0
1 gem installed
Installing ri documentation for rack-1.1.0...
Installing RDoc documentation for rack-1.1开发者_C百科.0...

But it always says that error. I have Rails 2.3.5 but I don't think the error is Rails related, but more like my server-related lol.

Thanks for help!

---

You installed Rack 1.1.0, the version required is 1.0.x.

$ gem uninstall rack
$ gem install rack -v 1.0.1

---

the above works, when installing, you have to indicate the version: "-v 1.0.1"

for some reason, it wont work otherwise.