When restoring a course from 1.5.4 to 1.8.1 that has and assignment type that is not installed in Moodle 1.8, like HSU's upload and review, Moodle allows the assignment to be created without any error or warning.
The assignment can't be deleted and the course can't be deleted because required files for deletion don't exist.
Error messages when deleting the assignment:
Warning: assignment_delete_instance(/home/lms/public_html/mod/assignment/type/uploadreview/assignment.class.php): failed to open stream: No such file or directory in /home/lms/public_html/mod/assignment/lib.php on line 1678
Fatal error: assignment_delete_instance(): Failed opening required '/home/lms/public_html/mod/assignment/type/uploadreview/assignment.class.php' (include_path='.:/usr/share/pear') in /home/lms/public_html/mod/assignment/lib.php on line 1678
email email@example.com for an example course with the problem. Unfortunately the zipped file is 43 mb, which is large r than I can upload.