ruby-1.9.2-p180 :007 > @data_objects.first
Mongo::OperationFailure: assertion db/key.cpp:409
    from /Users/joseph/.rvm/gems/ruby-1.9.2-p180@appname/gems/mongo-1.5.2/lib/mongo/cursor.rb:144:in `next'
    from /Users/joseph/.rvm/gems/ruby-1.9.2-p180@appname/gems/mongo-1.5.2/lib/mongo/collection.rb:288:in `find_one'
    from /Users/joseph/.rvm/gems/ruby-1.9.2-p180@appname/gems/mongoid-2.4.0/lib/mongoid/collections/master.rb:25:in `block in find_one'
    from /Users/joseph/.rvm/gems/ruby-1.9.2-p180@appname/gems/mongoid-2.4.0/lib/mongoid/collections/retry.rb:29:in `retry_on_connection_failure'
    from /Users/joseph/.rvm/gems/ruby-1.9.2-p180@appname/gems/mongoid-2.4.0/lib/mongoid/collections/master.rb:24:in `find_one'
    from /Users/joseph/.rvm/gems/ruby-1.9.2-p180@appname/gems/mongoid-2.4.0/lib/mongoid/collection.rb:60:in `find_one'
    from /Users/joseph/.rvm/gems/ruby-1.9.2-p180@appname/gems/mongoid-2.4.0/lib/mongoid/contexts/mongo.rb:191:in `first'
    from /Users/joseph/.rvm/gems/ruby-1.9.2-p180@appname/gems/mongoid-2.4.0/lib/mongoid/criteria.rb:45:in `first'
    from (irb):7
    from /Users/joseph/.rvm/rubies/ruby-1.9.2-p180/bin/irb:16:in `<main>'
rub