[General Omni Discussion] bassmanitram:
I know what did it now!

The Android Dev setup page lists the deps to install for Ubuntu 12.04 64-bit:

$ sudo apt-get install git gnupg flex bison gperf build-essential \
zip curl libc6-dev libncurses5-dev:i386 x11proto-core-dev \
libx11-dev:i386 libreadline6-dev:i386 libgl1-mesa-glx:i386 \
libgl1-mesa-dev g++-multilib mingw32 tofrodos \
python-markdown libxml2-utils xsltproc zlib1g-dev:i386

In a fresh VM I installed all of those practically one-by-one, omitting libgl1-mesa-glx:i386 (because I was suspicious about that one already). After a snapshot (to make my system easily recoverable) I attempted libgl1-mesa-glx:i386, and got this this time (I wish my home machine had responded similarly!)

Some packages could not be installed. This may mean that you have
requested an impossible situation or if you are using the unstable
distribution that some required packages have not yet been created
or been moved out of Incoming.
The following information may help to resolve the situation:

The following packages have unmet dependencies:
libgl1-mesa-glx:i386 : Depends: libglapi-mesa:i386 (= 8.0.4-0ubuntu0.7)
Recommends: libgl1-mesa-dri:i386 (>= 7.2)
E: Unable to correct problems, you have held broken packages.

So I THEN attempted the install (this time without completing, I assure you!) libglapi-mesa:i386 - and THIS is what it would have done had I continued:

Reading package lists... Done
Building dependency tree
Reading state information... Done
The following packages were automatically installed and are no longer required:
x11-apps g++-4.6 x11-session-utils g++-4.6-multilib x11-xfs-utils
libstdc++6-4.6-dev xinit libfs6 lib32stdc++6
Use 'apt-get autoremove' to remove them.
The following extra packages will be installed:
libgl1-mesa-glx libglapi-mesa xserver-xorg-core xserver-xorg-input-evdev
Suggested packages:
xfonts-100dpi xfonts-75dpi
The following packages will be REMOVED:
libegl1-mesa-drivers-lts-saucy libegl1-mesa-lts-saucy libgbm1-lts-saucy
libgl1-mesa-dri-lts-saucy libgl1-mesa-glx-lts-saucy libglamor-ltss0
libglapi-mesa-lts-saucy libopenvg1-mesa-lts-saucy libxatracker1-lts-saucy
ubuntu-desktop x11-xserver-utils-lts-saucy xorg xserver-common-lts-saucy
xserver-xorg-core-lts-saucy xserver-xorg-glamoregl-lts-saucy
xserver-xorg-input-all-lts-saucy xserver-xorg-input-evdev-lts-saucy
xserver-xorg-input-mouse-lts-saucy xserver-xorg-input-synaptics-lts-saucy
xserver-xorg-input-vmmouse-lts-saucy xserver-xorg-input-wacom-lts-saucy
xserver-xorg-lts-saucy xserver-xorg-video-all-lts-saucy
xserver-xorg-video-ati-lts-saucy xserver-xorg-video-cirrus-lts-saucy
xserver-xorg-video-fbdev-lts-saucy xserver-xorg-video-intel-lts-saucy
xserver-xorg-video-mach64-lts-saucy xserver-xorg-video-mga-lts-saucy
xserver-xorg-video-modesetting-lts-saucy
xserver-xorg-video-neomagic-lts-saucy xserver-xorg-video-nouveau-lts-saucy
xserver-xorg-video-openchrome-lts-saucy xserver-xorg-video-r128-lts-saucy
xserver-xorg-video-radeon-lts-saucy xserver-xorg-video-s3-lts-saucy
xserver-xorg-video-savage-lts-saucy
xserver-xorg-video-siliconmotion-lts-saucy xserver-xorg-video-sis-lts-saucy
xserver-xorg-video-sisusb-lts-saucy xserver-xorg-video-tdfx-lts-saucy
xserver-xorg-video-trident-lts-saucy xserver-xorg-video-vesa-lts-saucy
xserver-xorg-video-vmware-lts-saucy
The following NEW packages will be installed:
libgl1-mesa-glx libglapi-mesa libglapi-mesa:i386 xserver-xorg-core
xserver-xorg-input-evdev
0 upgraded, 5 newly installed, 44 to remove and 0 not upgraded.
Need to get 1,899 kB of archives.
After this operation, 31.4 MB disk space will be freed.
Do you want to continue [Y/n]?

i.e. destroyed X!!!

Any kernel devs been through this pain? (probably not the thread to ask that on, actually)

EDIT:

And I am not alone

Oh well