The latter is something that flight-safety people have been trying to fix for decades to no avail: when an autopilot decides it's stuck and decides to return manual control to the pilot, that usually means there's some kind of emergency in progress. An emergency the pilot is not fully informed about because, well, the autopilot was flying the plane and the pilot wasn't paying full attention. Oh, and doesn't have a full set of tools to address.
In this case, borked windowing system because of course that video driver that's the only #@%@# one on the planet that works with this old hardware should be discarded in favor of the minimal free one, which doesn't support 3D effects, which are no longer optional, so let's just start up the 3D subsystem anyway and see what happens when crucial parts of it hang.
There are tools to fix this (maybe) but I can't have them because part of the 14.04 installation process involves turning off all software sources not absolutely needed for the upgrade (because you're supposed to use Ubuntu Software Center. Except it won't work if anything goes wrong). Including proprietary drivers (natch) and also community-supported software like, say, synaptic or the configuration manager for the windowing system. Which I could turn back on from a text terminal if I knew where Canonical had decided to stash the info this week, which I can't easily find out because it's hard to run a browser without a windowing system.
It turns out that if I middle-click on the nonworking desktop I can open up a borked wallpaper chooser, which can in turn be converted to a borked preference pane from which I can get to the pref for software sources and turn damn-all everything back on. At which point I can download the stuff I want, switch to a working driver, reconfigure compiz and unity to have the crap I need and not load the plugin that always hangs. And now I can download the new copies of the software I need to use.
Oh, and someone please remind me to reset the baud rates on all the USB connections to integer multiples of 9600, because apparently there's a component that crashes if you use numbers like 250000. (I found that out on my office machine, where the upgrade otherwise went swimmingly but the control software for my 3D printer kept turning itself off.)