by William Voyek.
Thank you so much for your help, Lawrence.
I really wish that the developers (since they decided not to fix 2.3 [even though it was the current release at the time]) would have at least included a patch for 2.3 that warned users of this issue when doing a backup of a course with the database enrollment plugin activated.
I think another poster may be having the same issue. I think I will post a link to this thread for him.