by Chester Folming.
Well I am sorry I was a little sloppy - I was refering to the ldap mapped ID number. If you go to the individual user you will need him/her to have a unique number.
So if you go to the users profile page you can see if this is unique. We had some users that somehow was created wrong and they got the ID number 999999. And they misbehaved..
The other option is important too - that this user does not have both editing teacher (tutor) and student rights in the course since this could create a conflict. Editing teachers have a difference in permission on mod/assign:grade - where this is allowed for editing teacher but not for students.