The term permission list sounds like a list that contains all possible permissions that one can choose from with regard to a particular system. For example, a Unix file permission list would be a list that contains all possible variations one can come up with to specify which users or system processes are granted access to his or her files. If you're at all familiar with Unix systems, this would be a set of permission bits you attach to a file that limits other users' access to it for reasons of security. And that's exactly what an ACL that other people here have been talking about is. I think, in your case, however, these would sound a lot better:
Unable to load the trusted users list.
Unable to load the authorized users list.
In the field of information systems, trusted or authorized users would be users who have been given permission to use a certain functionality of the system by granting them a set of permissions that allow them to do that.