Comment 20 for bug 767927

The key is to run "sudo apt-get purge v86d" - Daniel try this command

If I install that package (v86d) and execute /sbin/v86d, the console will lock up immediately when switching VTs. v86d is not included by default on a fresh stock Ubuntu install.

It's also a good idea to set the Plymouth theme back to default, if you changed it....

sudo update-alternatives --config default.plymouth