Stack level too deep upgrading to Rails 3 - ruby-on-rails

Question

I'm upgrading an app to Rails 3 and have been going through it bit by bit, for example replacing all the old plugins with the relevant gems in the gemfile.
I seem to have got stuck however because now whenever I try to run the server I get this:
=> Booting WEBrick
=> Rails 3.0.0 application starting in development on http://0.0.0.0:3000
=> Call with -d to detach
=> Ctrl-C to shutdown server
Exiting
/Users/camillavk/.rvm/gems/ruby-1.9.3-p551#rails3/gems/rack-1.2.8/lib/rack/builder.rb:35: stack level too deep (SystemStackError)
I've been googling it for ages and have come to the conclusion that it is still because of one of the plugins, I just can't figure out which one. I have removed each one individually but none of them makes a difference.
I found these three similar questions but they don't really help me....
Stack level too deep error after running bundle update
SystemStackError at the rack level in Ruby 1.9.2, not 1.8.7
Stack level too deep trying to update from 3.0 to 3.1
My gemfile looks like this at the moment:
source 'https://rubygems.org'
gem "rails", "3.0.0"
#need to replace old acts_as_commentable vendor plugin
gem 'acts_as_commentable', '3.0.1'
gem "airbrake"
#need to add authlogic gem
gem 'authlogic', '~> 2.1.6'
gem "aws-s3"
gem "bj"
gem "bundler", "~> 1.0.0"
gem "calendar_date_select", "1.15"
gem "cancan", "1.2.0"
gem "carmen"
#replace plugin casein?
gem 'casein', '3.1.0'
gem 'comma', '0.4.1'
gem 'exifr'
# factory_girl 1.2.4 wasn't working with Rails 3 - consider an upgrade to factory_girl_rails?
# gem "factory_girl", "1.2.4"
gem 'fastercsv'
gem "geokit"
#need to replace above with below
gem 'geokit-rails'
gem "haml"
gem "hpricot"
gem 'hoptoad_notifier'
gem "jrails"
gem "libxml-ruby", "2.4.0"
gem "memcached", "~> 1.8.0"
#memcached no longer works?
gem 'dalli'
# Not sure why we have this if we're using SQLite3
gem "mysql2", "~> 0.2.6"
#TODO: changed by almazom
gem "rake", "0.8.4"
gem 'recurly'
gem "rdoc"
gem "rmagick"
gem "rspreedly"
gem "rubyzip"
gem 'sass'
# searchlogic not supported for rails3
# gem 'searchlogic'
gem 'rd_searchlogic', :require => 'searchlogic', :git => 'git://github.com/railsdog/searchlogic.git'
#need to use simplecov when upgrading to ruby 2 as rcov doesn't work
gem "simplecov"
gem 'sqlite3'
# tmail no longer included in rails 3?
gem 'tmail'
#need to upgrade will_paginate for casein...?
# gem "will_paginate", "2.3.16"
gem 'will_paginate', '3.0.4'
gem 'yaml_db'
group :development, :test do
gem 'test-unit', '1.2.3'
gem 'rspec', '1.3.2'
gem 'rspec-rails', '~> 1.3.4'
end
group :test do
gem 'capybara', '0.3.5'
gem 'cucumber', '1.1.2'
gem 'cucumber-rails', :git => "git://github.com/RKelln/cucumber-rails.git", :branch => "0.3.2-capybara-fix"
gem 'database_cleaner'
end
And the plugins I have are:
acts-as-favorite-updated
acts_as_configurable
acts_as_follower
better_logging
concerned_with
default_value_for
fast_context
fetcher
has_many_friends
jrails
paperclip
parallel_tests
rails_upgrade
yaml_db
Does anyone have any idea how I can deal with this issue?? :-(