纸夹无法保存附件

I'm using Ruby 1.9 and Rails 2.3.4 with Paperclip gem to save attachments. and I followed tutorial by adding the proper migration, adding (has_attached_file :video) to the model, making the form (multipart) and adding <%= f.file_field :video %> to it...I'm using Ruby 1.9 and Rails 2.3.4 with Papercl