Ethernet cannot connect to 802.1X authentication

We've always had problems with getting Ubuntu boxes to connect to our 802.1X authenticated ethernet, but those problems have usually been fixable by a shotgun-approach of restarting network-manager, unplugging the ethernet cable and re-inserting it, prodding gnome-keyring-daemon, and repeating several times until finally the connection is made. Unfortunately, with Ubuntu 13.04 we've finally reached the point where we can't get our boxes to connect at all.

Our older boxes (12.10 and back) are still able to connect, but after updating - and then clean-installing - to Ubuntu 13.04, I'm just continually prompted for my password (verified correct on other boxes), and the connection never completes.

/var/log/syslog says : "<warn> Activation (eth0/wired): association took too long."