The issue, by the way, is the Zenbook (UX31A) not liking the new kernel. The solution is Joseph Salisbury's inofficial kernel fix.
First thing: get a command line and an internet connection. For this, I booted into Recovery Mode and chose the 'root' option.
mount -o remount,rw /
#cd into some convenient directory, as we're writing a file next
wpa_passphrase <essid> <passphrase> > wpa.conf
ifconfig wlan0 up
#if you don't know your driver (mine is the generic wext),
#try 'wpa_supplicant --help'
wpa_supplicant -Dwext -iwlan0 -cwpa.conf &
dpkg -i linux-image-3.11.0-12-generic_3.11.0-12.19~lp1195483v2_amd64.deb linux-image-extra-3.11.0-12-generic_3.11.0-12.19~lp1195483v2_amd64.deb
I exited the rescue system and rebooted (note: the 'resume' option doesn't work yet, you need a proper shutdown) and got my system back. Hooray!
The new kernel needs to be protected against upgrades:
sudo apt-mark hold linux-image-3.11.0-12-generic
sudo apt-mark hold linux-image-extra-3.11.0-12-generic
- Recovery mode: wiki.ubuntu.com/RecoveryMode
- WPA from command line: linux.icydog.net/wpa.php, askubuntu.com/questions/104066/enable-wifi-in-recovery-terminal
- Kernel fix: bugs.launchpad.net/ubuntu/+source/linux/+bug/1195483