Rails 3.2 NoMethodError (undefined method `name' for nil:NilClass): Carrierwave

I've implemented file upload with carrierwave in at least 5 different places across my app. They all work well. Until the most recent implementation... on save in the create method I get the following exception:

NoMethodError (undefined method name' for nil:NilClass):
app/controllers/downstream_documents_controller.rb:34:increate'

I can't figure this one out. The code was pulled from a previous file upload which currently works just fine. I simply changed the model names appropriately.

Here is my Model code:

class DownstreamDocument < ActiveRecord::Base
  attr_accessible :company_id, :created_by, :updated_by, :document_title, :document_type_id, :downstream_id, :file_name, :is_active


  # set schema name and table name for TakebackDB  
  self.table_name = "track.DownstreamDocument"

  mount_uploader :file_name, DownstreamDocumentUploader

  default_scope where(:is_active => true)

  belongs_to :company, :foreign_key => "company_id"

end

And uploader:

# encoding: utf-8

class DownstreamDocumentUploader < CarrierWave::Uploader::Base

    # Include RMagick or MiniMagick support:
  include CarrierWave::RMagick
  # include CarrierWave::MiniMagick
  include CarrierWave::MimeTypes
  # Choose what kind of storage to use for this uploader:
  storage :azure
  # storage :fog

  # Override the directory where uploaded files will be stored.
  # This is a sensible default for uploaders that are meant to be mounted:
  def store_dir
   "#{model.class.to_s.underscore}/#{mounted_as}/#{model.company_id}"
  end

  # Provide a default URL as a default if there hasn't been a file uploaded:
  # def default_url
  #   # For Rails 3.1+ asset pipeline compatibility:
  #   # ActionController::Base.helpers.asset_path("fallback/" + [version_name, "default.png"].compact.join('_'))
  #
  #   "/images/fallback/" + [version_name, "default.png"].compact.join('_')
  # end

  # Process files as they are uploaded:
  # process :scale => [200, 300]
  #
  # def scale(width, height)
  #   # do something
  # end

 def cover 
    manipulate! do |frame, index|
      frame if index.zero?
    end
  end   


  # Create different versions of your uploaded files:
   version :thumb do
     process :cover
     process :resize_to_limit => [100, 100]
     process :convert => 'jpg'  
     process :set_content_type

    def full_filename (for_file = model.source.file)
      super.chomp(File.extname(super)) + '.jpg'
     end

   end


  # Change Image to JPEG
  def set_content_type(*args)
     self.file.instance_variable_set(:@content_type, "image/jpg")
  end





  # Add a white list of extensions which are allowed to be uploaded.
  # For images you might use something like this:
   def extension_white_list
     %w(jpg jpeg gif png pdf)
   end

  # Override the filename of the uploaded files:
  # Avoid using model.id or version_name here, see uploader/store.rb for details.
  # def filename
  #   "something.jpg" if original_filename
  # end

end

And my controller:

class DownstreamDocumentsController < ApplicationController


load_and_authorize_resource 

respond_to :html, :js



def index

@downstream_id = params[:downstream_id]
@downstream = Company.find(@downstream_id)  
@documents = DownstreamDocument.where(:company_id => current_user.company_id, :downstream_id => @downstream_id )   

end



def create

  @downstream_document = DownstreamDocument.new(file_name: params[:file])
  @downstream_document.created_by = current_user.user_name
  @downstream_document.updated_by = current_user.user_name

  @downstream_document.downstream_id = params[:downstream_id]
  @downstream_document.company_id = params[:company_id]
  @downstream_document.document_title = params[:file]
  @downstream_document.document_type_id = 1
  @downstream_document.is_active = params[:is_active]



  if @downstream_document.save!
    #do some stuff
    @downstream = Company.find(@downstream_document.downstream_id)
    @documents = DownstreamDocument.where(:company_id => current_user.company_id, :downstream_id => @downstream_id )   

   # render json: { message: "success", company_profile_document: @company_profile_document, 
   #   company_profile: @company_profile }, :status => 200
   # else
   #   render json: { error: @image.errors.full_messages.join(',')}, :status => 400  
   # end

    respond_to do |format|
        format.json{ render :json => @documents }
      end
  end


end

def update

end

def delete

end


end

The exception is thrown in the controller's create method on if @downstream_document.save!

All the variables for @downstream_document appear to be populated correctly prior to the save call.

If I've got a typo or syntax error, I'm not seeing it. Any help would be appreciated!

Thanks in advance... I've been staring at this for way too long and need a new pair of eyes on it.