Adding some info that maybe you can use.
In "my site forum", when I press "member list" button, it reset´s all the portal user settings in user accounts, it´s not happening when I go ADMIN - FORUM USERS, but again, in MEMBER LIST BUTTON.
My problem is not creating add/edit threads, but manage forum/groups in ADMIN, it happen´s when I edited/managed some foruns privacy and permissions in start when it was working or when I used SQL script from Crysp to correct the rates and member list that makes the rate work fine, but not the member list
So, Im not able anymore to CREATE AND EDIT FORUM/GROUPS, that means, set permission, and configure privacy, etc...
My module settings is checked "view for all user´s" ONLY, admin have all the check box set like default and non editable, so, I think it´s all right here in module settings unless you say Im not.
And like all, I cant start/create thread in here DNN site forum.