I am testing some settings for Teachers.
I have Teacher menu link set up to display for teacher group only & assumed that as i was logged in as a super admin that I would see the teacher link, but I didn't.
Via Components > Guru > Teacher Manage Teacher, I added a new teacher using the "Existing User" button.
Found myself (Super Admin) & then added myself as a teacher.
Upon submitting this, I was logged out & can now no longer login the backend of the site.
Further testing & checking shows that I am no longer a super admin & now only assigned to the teacher group.
IMHO this is a flaw & bug that needs fixing. I personally know how to reset myself as a super admin, but this shouldn't have happened.