by Dan Marsden.
Hi Teddy,
the insitutional check error is because you have ticked the "institutionnode" checkbox on the turnitin settings page - uncheck it and save.
the class already exists error is harder to get rid of - easiest option is to create a new Moodle course based on your old one and delete the old one. Harder options involve modifying the database and a good knowledge of the Turnitin API and the code.
