I have been battling with this question for the past couple of days. I have never been fortunate enough to have to install a Rails application on production and have been pulling my hair out over these errors. My application is currently running http://typealoud.com and throwing an exception which basically amounts to a "LoadError" in a controller that is, well, very basic.
I do have an existing application running that only contains a welcome controller, and this application is a mirror of the settings (with the paths changed, obviously). I came across a few articles explaining that when using RVM you need to set some environment variables for Passenger to read the ruby gem repositories correctly, but I am not using RVM (Ruby Enterprise Edition, latest release).
I am currently using a edge (master branch) of two popular gems: warden and devise which my UsersController inherits from the Devise::UsersController. Both of these gems work correctly in development mode. I have a special user (op) that both applications run under and thus in order to get this functionality with a Rails 3 Rack application the config.ru file is owned by that user. I have checked out all the necessary gems through the bundler as this user.
Has anyone ran into a similar problem? I have no objections to posting any code or configuration files, everything is real straight forward and basic.