When I use two Queries and iterate() over the results, the second one fails with a PHP Fatal error (ReflectionException). It has a strange message ('Class does not exist').
This happens with any two different entities. The error seems to occur when next() is called (directly or via foreach) and the objects are being created.
$q = $em->createQuery('SELECT c FROM Entity\Country c');
$q = $em->createQuery('SELECT u FROM Entity\User u');
$q->iterate()->next(); // FAILS