Right after updating Mongrel, gem_plugin and some other (probably unrelated) gems today, Mongrel didn’t like me any more, refusing to start up any Rail s application. Instead, I got this nice message complaining about a missing init.rb in the activerdf gem:

** Rails loaded. ** Loading any Rails specific GemPlugins Exiting /usr/local/lib/site_ruby/1.8/rubygems/custom_require.rb:27:in 'gem_original_require': no such file to load -- /usr/lib/ruby/gems/1.8/gems/activerdf-1.6.1/lib/activerdf/init.rb (MissingSourceFile)

It took me a while to find the fix on rubyforge via google, so maybe this helps somebody else having the same problem.