Bad ubuntu

Ubuntu has been lax in its software testing - in the last few days it rolled out a broken X.org x-server package which renders PCs console-only upon reboot. Thinking it was something I'd done I spent some time trying old kernels etc. - eventually I found an article explaining the cause and solution (using apt to downgrade to an older version). Unfortunately another bug also cropped up as a result of this - Python/Tkinter no longer works. It gives an obscure error message about not knowing what colour "Black" is and dies. I finally tracked this down (with Google) to changes I'd made to xorg.conf while trying to fix it.