After installing the question-type "jme" it's not possible to save such a question in a quiz.

I think there's a problem with the installation and the database: a "prefix_jme" table is created, but moodle expects a "prefix_question_jme". I changed the name of the table manually and then it works.
Maybe this problem is because of the file postgre7.php (without s) in the db-directory of jme. In all other question-types it is called postgres7.php (with s).