Suddenly, I noticed that all of my BO AccessLevel attribute default values had been changed to Administrator. The system is doing this on its own. Kind of a big problem.
To duplicate, I just have to add a BO to the System User and Viola! All AccessLevel attributes have their default values changed to Administrator. When a BO is removed from the System User group, the same joy is experienced.
I'm on 4.6 Build 1206