AJAX file upload using Remotipart and Carrierwave

Question

I have a model that has an icon associated to it. This icon upload is managed by Carrierwave.

My issue arises when I try to send the file via ajax from my form.

My Model is as follows:

class Category < ActiveRecord::Base

   attr_accessible :name,
                   :icon
   mount_uploader :icon, TemplateCategoryIconUploader

 end

Controller action:

def update
    @category = Category.find(params[:id])
    @category.update_attributes(params[:category])

    if @category.save
      flash[:notice] = "Category Updated!"
      render_ajax_content_replace :element => :show_category, :partial => 'show'
    else
      render_ajax_content_replace :element => :show_category, :partial => 'show'
    end
  end

And finally my form:

<%= form_for @category, :html => {:multipart => true}, :remote => true do |f| %>

        <%= error_messages_for f.object %>

       <%= f.file_field :icon %>
<% end %>

Removing the ajax side of thing allows the submit to work. However I require it to be done with AJAX.

The error I get is a missing template error. However all my partials exist and work. For some reason the render_ajax_content_replace breaks. Its simply supposed to replace an element with a partial. This works perfectly everywhere else. Adding AJAX files breaks it.