See issue 14643 for details:
1.- Assigned cups printer to terminal mac address.
2.- UserA connects to thinlinc. File printers.conf is updated accordingly: AllowUser UserA is added. I can see all printers on the server, though. I have access to the one assigned to the terminal only.
3.- Closed the session. printers.conf is not updated.
4.- Reopen the session from the same terminal (same mac address), login with UserB. Printers.conf is not updated. I cannot print.