We just upgraded our virtual machines to what I thought was an identical ruby configuration (via RVM... Ruby 1.9.2, Rails 3.0.7, DataMapper 1.1.0). The biggest difference w
Psych is the new YAML parser which is presumably better but can't merge hash keys.
This should help http://pivotallabs.com/users/mkocher/blog/articles/1692-yaml-psych-and-ruby-1-9-2-p180-here-there-be-dragons
Since you have done an upgrade it may be that your database permissions have messed up. Try viewing that you have the necessary permissions i.e the machine on which the code resides has privileges to connect and modify on the database machine. Looking at you database.yml it should be something like"
GRANT ALL PRIVILEGES ON productionbd.* to 'user'@'<app-server-ip>' identified by 'pass';