Redmine suddenly stopped working. How to troubleshoot?

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http://serverfault.com – I was a happy user of redmine for like 6 months. My plan was to set it up and never update anything in order not to deal with dependencies and stuff. I'm using Ubuntu server 10.04 (Apache/Passenger) with disabled all kinds of updates. This morning I started getting Internal Error in browser. Log file says something like: Processing WelcomeController#index (for at 2012-03-05 10:44:12) [GET] Parameters: {"action"=>"index", "controller"=>"welcome"} NoMethodError (undefined method `[]' for nil:NilClass): /app/models/setting.rb:100:in `value=' /vendor/rails/activer (HowTos)