I was having the same issue on an external wireless adapter. It would try to connect to local APs that I had previously connected to or tried to connect to. The below solution (deleting the SSID from /etc/NetworkManager/system-connections) fixed my problem.
http://askubuntu.com/questions/120415/how-to-remove-access-point-from- saved-list -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1063358 Title: Wireless authentication required dialog opens multiple times To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/network-manager-applet/+bug/1063358/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
