We are currently using Moodle 2.1.1+ (Build: 20110916) with database enrollment and the sync.php script to update Moodle with the database on a regular basis. Users are correctly enrolled and unenrolled using this method. However, what we've been finding is that users will be correctly unenrolled from the course (they no longer show up under enrolled users) but they do still show up in the participants list and in the gradebook. Even when the user logs in, the course is still shown in their active list.
Does anyone have ideas of why this might be occurring? I've verified that the external unenroll action is set to "Unenroll user from course." I can't find any references to it in the forums or bugtracker. If I can provide any additional information that would be of help, let me know.