Application.rb methods not accessible

For some reason I seem to be unable to call methods defined in
application.rb

All controllers are supposed to inherit from application.rb correct?

I have a bit of code that does some filtering and I want it accessible
from any controller however when I try to call it, it fails.

show how you've defined it in application.rb and how you're calling
from your controller.

application.rb
  def desired_columns(model, fields, omit = true)
    columns = model.constantize.content_columns.collect do |
content_column|
      if omit
        for field in fields
          if content_column.name != field
            content_column
          end
        end
      else
        for field in fields
          if content_column.name == field
            content_column
          end
        end
      end
    end

    return columns.compact!
  end

Here is where I'm calling it this is in a controller:

  def details
    @user = session[:user]

    @columns = desired_columns("User", ["salt", "hashed_password"])
  end

that looks correct... make sure your application.rb starts with
  class ApplicationController < ActionController::Base

and other controllers start with
  class MyController < ApplicationController

what version OS/ruby/rails? i'd probably back up my project, nuke
ruby and rails and reinstall them.