NoMethodError: private method `write_uploader' backtrace

gistfile1.txt

NoMethodError: private method `write_uploader' called for #<Item:0x007fd71682aa60>
	from /usr/local/rvm/gems/ruby-1.9.2-p290/gems/activemodel-3.1.1/lib/active_model/attribute_methods.rb:385:in `method_missing'
	from /usr/local/rvm/gems/ruby-1.9.2-p290/gems/activerecord-3.1.1/lib/active_record/attribute_methods.rb:60:in `method_missing'
	from /usr/local/rvm/gems/ruby-1.9.2-p290/gems/carrierwave-0.5.7/lib/carrierwave/mount.rb:299:in `write_identifier'
	from /usr/local/rvm/gems/ruby-1.9.2-p290/gems/carrierwave-0.5.7/lib/carrierwave/mount.rb:229:in `write_file_identifier'
	from /usr/local/rvm/gems/ruby-1.9.2-p290/gems/activesupport-3.1.1/lib/active_support/callbacks.rb:413:in `_run_save_callbacks'
	from /usr/local/rvm/gems/ruby-1.9.2-p290/gems/activesupport-3.1.1/lib/active_support/callbacks.rb:81:in `run_callbacks'
	from /usr/local/rvm/gems/ruby-1.9.2-p290/gems/activerecord-3.1.1/lib/active_record/callbacks.rb:264:in `create_or_update'
	from /usr/local/rvm/gems/ruby-1.9.2-p290/gems/activerecord-3.1.1/lib/active_record/persistence.rb:57:in `save!'
	from /usr/local/rvm/gems/ruby-1.9.2-p290/gems/activerecord-3.1.1/lib/active_record/validations.rb:56:in `save!'
	from /usr/local/rvm/gems/ruby-1.9.2-p290/gems/activerecord-3.1.1/lib/active_record/attribute_methods/dirty.rb:33:in `save!'
	from /usr/local/rvm/gems/ruby-1.9.2-p290/gems/activerecord-3.1.1/lib/active_record/transactions.rb:246:in `block in save!'
	from /usr/local/rvm/gems/ruby-1.9.2-p290/gems/activerecord-3.1.1/lib/active_record/transactions.rb:295:in `block in with_transaction_returning_status'
	from /usr/local/rvm/gems/ruby-1.9.2-p290/gems/activerecord-3.1.1/lib/active_record/connection_adapters/abstract/database_statements.rb:192:in `transaction'
	from /usr/local/rvm/gems/ruby-1.9.2-p290/gems/activerecord-3.1.1/lib/active_record/transactions.rb:208:in `transaction'
	from /usr/local/rvm/gems/ruby-1.9.2-p290/gems/activerecord-3.1.1/lib/active_record/transactions.rb:293:in `with_transaction_returning_status'
	from /usr/local/rvm/gems/ruby-1.9.2-p290/gems/activerecord-3.1.1/lib/active_record/transactions.rb:246:in `save!'
	from (irb):17
	from /usr/local/rvm/gems/ruby-1.9.2-p290/gems/railties-3.1.1/lib/rails/commands/console.rb:45:in `start'
	from /usr/local/rvm/gems/ruby-1.9.2-p290/gems/railties-3.1.1/lib/rails/commands/console.rb:8:in `start'
	from /usr/local/rvm/gems/ruby-1.9.2-p290/gems/railties-3.1.1/lib/rails/commands.rb:40:in `<top (required)>'
	from script/rails:6:in `require'