Using 2.5.2+ (20130913).
On duplicating any course item, get a white screen or a out of memory error. I raised my memory limit from 256M to 512M and still got the same thing.

1. Create new course.
2. Create a new quiz.
3. Duplicate new quiz.

Here is a sample of what I can get from debugging before it runs out of memory.

Error: mdb->get_record() found more than one record!

line 1409 of /lib/dml/moodle_database.php: call to debugging()
line 1470 of /lib/dml/moodle_database.php: call to moodle_database->get_record_sql()
line 3387 of /backup/moodle2/restore_stepslib.php: call to moodle_database->get_field_sql()
line 131 of /backup/util/plan/restore_structure_step.class.php: call to restore_create_categories_and_questions->process_question_hint()
line 103 of /backup/util/helper/restore_structure_parser_processor.class.php: call to restore_structure_step->process()
line 151 of /backup/util/xml/parser/processors/grouped_parser_processor.class.php: call to restore_structure_parser_processor->dispatch_chunk()
line 91 of /backup/util/helper/restore_structure_parser_processor.class.php: call to grouped_parser_processor->postprocess_chunk()
line 148 of /backup/util/xml/parser/processors/simplified_parser_processor.class.php: call to restore_structure_parser_processor->postprocess_chunk()
line 92 of /backup/util/xml/parser/processors/progressive_parser_processor.class.php: call to simplified_parser_processor->process_chunk()
line 169 of /backup/util/xml/parser/progressive_parser.class.php: call to progressive_parser_processor->receive_chunk()
line 253 of /backup/util/xml/parser/progressive_parser.class.php: call to progressive_parser->publish()
line ? of unknownfile: call to progressive_parser->end_tag()
line 158 of /backup/util/xml/parser/progressive_parser.class.php: call to xml_parse()
line 137 of /backup/util/xml/parser/progressive_parser.class.php: call to progressive_parser->parse()
line 105 of /backup/util/plan/restore_structure_step.class.php: call to progressive_parser->process()
line 153 of /backup/util/plan/base_task.class.php: call to restore_structure_step->execute()
line 163 of /backup/util/plan/base_plan.class.php: call to base_task->execute()
line 157 of /backup/util/plan/restore_plan.class.php: call to base_plan->execute()
line 315 of /backup/controller/restore_controller.class.php: call to restore_plan->execute()
line 101 of /course/modduplicate.php: call to restore_controller->execute_plan()

Oddly enough, the item does get duplicated, but you are not given the chance to edit it.
/backup/controller/restore_controller.class.php is the only one of these files that appears changed from this update, but the changes don't seem to be what caused this. Not sure when this was first broken.

I looked through other tickets and didn't find one that seemed to hit on this quite the same.