when we went live this morning, the old login wouldn't work so siggy reset it. But now I'm trying to set up new administrators and when i click save, nothing happens. it appears that we have no admins

I looked into natalie's problem, it was not directly a bug but some architectural inconsistency that needs to be solved on the long run:
She was using Object::useCustomClass("Member", "MyMember"), which lead SecurityAdmin only to show members of this subclass (they were actually added fine). While this is desireable in some scenarios (e.g. automatically creating a ForumMember instead of a Member), its nothing you want in SecurityAdmin #)