If someone encounters a display while using X that does not refresh and
seems the computer is locked up. It is not locked up, but the display is.
It is still possible to switch to a terminal and safely shut down your
computer. I think reboot or poweroff would safely shutdown or reboot
your computer.
I filed this bug regarding the twice encountered screen lockup.
This is mainly posted for the two hours before the computer locks up.
... The display, yes! Computer no!
https://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=128358
I hope this reduces the chances of people just killing their computers
when process are still running fine.
Jim