This bug is probably a duplicate of bug #37678 or bug #26513 and upstream https://bugs.freedesktop.org/show_bug.cgi?id=5986, all well known for a long time. Other than the workaround I sketched above, you can use the alternate install cd.
It should be tested if disabling Composite is another, better workaround. It is possible that this bug is limited to AMD systems, I can not see any reliable confirmation from any Intel users. -- [edgy][regression][rv280] black screen and console freeze when X starts - drm lockup https://launchpad.net/bugs/67487 -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
