It was a struggle, but we got there in the end. The background to this was that I tried to upgrade my Rails install from 2.3.3 to 2.3.5 using the Rails wiki Getting Started guide, and then started running into problems. Ooh look, here it is:
Library/Ruby/Site/1.8/rubygems.rb:777:in `report_activate_error’: RubyGem version error: rack(1.0.0 not ~> 1.0.1) (Gem::LoadError)
…which [...]