Stack level too deep trying to update from 3.0 to 3.1

问题

I'm getting this error while trying to run 'rails s' after upgrading update from rails 3.0.10 to 3.1.0

~/.rvm/gems/ruby-2.0.0-p353/gems/rack-1.3.10/lib/rack/builder.rb:40: stack level too deep (SystemStackError)

Has anyone else run into this and solved the problem? Google search yields nothing except that it might involve gem dependencies.

来源：https://stackoverflow.com/questions/20725283/stack-level-too-deep-trying-to-update-from-3-0-to-3-1