Ok, so it looks like this may be a duplicate of bugs 46874 and 30447. Although here it is happening with the OSS i915/i810 graphics driver combination.
I'm going to try the workaround of disabling the "usplash" that is mentioned in one of the above bug #'s. -- consistent crash on logout, restart or shutdown from X https://launchpad.net/bugs/58425 -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
