First of all: none of this is an issue if I’m logged in as an Admin. All works fine.

But, if I’m logged in as someone from the Member group and I try to access a standalone entry form, the attached file upload button takes me to another login screen. When I enter my login info here (again) I’m told “You are not authorized to perform this action”. However, if I go and change the Member group preferences so that group members can login to the control panel, this login screen that I arrived at from clicking the file upload button will then log me into the control panel. What’s the deal? I’ve set the Member group to have privileges of file upload in the control panel, too.