https://bugzilla.kernel.org/show_bug.cgi?id=62721
--- Comment #14 from Jason Vas Dias jason.vas.dias@gmail.com --- When the lockup happens, the <CTRL>+<ALT>+<F{N}> VT switch keys also stop working, and the only way to access the machine is to SSH in from another host.
I was going to report this as an Ubuntu bug, but it appears to be an upstream bug - or should I report this on Ubuntu as well ?