can't activate rack problem while install spree commerce

I install spree version 0.9.4 with gem install spree and run a set up command spree mystore and get this errors messages. Have anybody experienced this whether in spree or not ?

D:\Workspaces>spree mystore
C:/Program Files/BitNami RubyStack/ruby/lib/ruby/site_ruby/1.8/rubygems.rb:280:i
n `activate': can't a开发者_StackOverflowctivate rack (>= 1.0.1, runtime) for ["spree-0.9.4"], alrea
dy activated rack-1.0.0 for ["actionpack-2.3.5", "rails-2.3.5", "spree-0.9.4"] (
Gem::LoadError)
        from C:/Program Files/BitNami RubyStack/ruby/lib/ruby/site_ruby/1.8/ruby
gems.rb:296:in `activate'
        from C:/Program Files/BitNami RubyStack/ruby/lib/ruby/site_ruby/1.8/ruby
gems.rb:295:in `each'
        from C:/Program Files/BitNami RubyStack/ruby/lib/ruby/site_ruby/1.8/ruby
gems.rb:295:in `activate'
        from C:/Program Files/BitNami RubyStack/ruby/lib/ruby/site_ruby/1.8/ruby
gems.rb:68:in `gem'
    from C:/Program Files/BitNami RubyStack/ruby/bin/spree:18

Thanks

I found similar problems (with difference gem) all over the places and decided to solve it by install a new gem, and uninstall the old one

gem uninstall rack -v 1.0.0

then

gem install rack -v 1.0.1

hope this helps those who have similar problem.

p.s. see someone posting about freezing rails, but I didn't dig into it yet.

It appears spree requires v1.0.1, whereas rack is now at version 1.1.0. Please install 1.0.1, the pain will go away.