SQL error on install, inoperative after

When I enabled the menu per role module, I got this error:

All parts of a PRIMARY KEY must be NOT NULL; If you need NULL in a key, use UNIQUE instead query: CREATE TABLE if not exists menu_per_role ( mid int(10) unsigned, rid int(10) unsigned, PRIMARY KEY(mid, rid) ) TYPE=MyISAM /*!40100 DEFAULT CHARACTER SET utf8 */; in /var/www/html/drupal/includes/database.mysql.inc on line 172.

So I went in by hand, and ran this:

CREATE TABLE if not exists menu_per_role ( mid int(10) unsigned NOT NULL, rid int(10) unsigned NOT NULL, PRIMARY KEY(mid, rid) ) TYPE=MyISAM /*!40100 DEFAULT CHARACTER SET utf8 */;

No further errors, but when I set permission on a menu item... nothing happens! The item still appears for all users.