Can't Dump file - paperclip with workling and starling

here is my controller action:

def create    UploadWorker.async_send_file(params[:image])

flash[:notice] = "uploading file" redirect_to root_url end

class UploadWorker < Workling::Base   def send_file(options)      @image = current_user.images.build(params[:image])      @image.save   end end

I would like the paperclip upload, conversion and save to take place in the background. The error I get:

can't dump File

/usr/lib/ruby/gems/1.8/gems/memcache-client-1.8.5/lib/memcache.rb:360:in `dump' /usr/lib/ruby/gems/1.8/gems/memcache-client-1.8.5/lib/memcache.rb:360:in `set_without_newrelic_trace' (eval):5:in `set' (eval):4:in `set' app/controllers/images_controller.rb:52:in `create'

{"commit"=>"upload", "authenticity_token"=>"3JniM+vyc29t+23lnQjm0RNjrzV37YswhK/fauMfEZY=", "image"=>{"photo"=>#<File:/tmp/RackMultipart20100814-12328-bwjqb8-0>, "location"=>"", "uid"=>"upload_workers:send_file:37ec9541ff9c36d5a7ac802822316d77", "description"=>"", "state_id"=>"1"}}