Re: Spring cleaning time
Ubuntu is sometimes it's own worst enemy.
It's actually very good at telling you that there are proprietary binary drivers available for your video card, and telling you what you need to do to enable the non-free repository and switching to the driver.
Unfortunately, it's not very good at telling you that the new binary driver you've just installed as part of the update has dropped support for your graphics card. The result, you put the update on, reboot the system, and hey presto, you're back in un-accelerated 640x480 16 colour world, or if you're very lucky 800x600 VESA mode, whichever is the lowest common denominator. But you should get some sign of the screen working, even if it's just text-mode.
The solution is to remove the nvidia or ATI fglx drivers, and install either the nv or nouveau driver for nvidia cards or the radeon driver for ATI cards. Nouveau and radion both provide some 3D function, although it's likely to not be as good as the binary driver (but still perfectly adequate for 2D work and even things like Google Earth).
Another solution is to work out which the last binary driver supported your card, and back-level the package to that, or even add the repository for the earlier release and back level, and then freeze those packages. But this later option can sometimes lead to strange booting effects, especially if the KMS support for the cards has changed.
BTW, a fresh install would probably just work.