[CentOS] suddenly X gives black screen with small clock cursor

Fri Oct 11 09:50:14 UTC 2013
John Doe <jdmls at yahoo.com>

From: Fred Smith <fredex at fcshome.stoneham.ma.us>

>  I rebooted a while ago (and in between the down and up, I installed Fedora
>  20 Beta on a USB hard drive, making sure it wouldn't mess with my 
> Centos  system). The install went fine, but afterwards, when I reboot Centos, it
>  comes up with a black screen and a clock as the mouse cursor (small clock).
>     chmod a+rw /dev/null
>     chmod a+rw /dev/urandom
>     chmod a+rw /dev/zero
>     chmod a+rw /dev/full
>     chmod a+rw /dev/random
> Can anyone suggest an accurate way to have the system fix all the permissions
> in /dev? some arcane options on rpm, perhaps?

Nothing at all in the logs...?
Global check: rpm -qVa
Maybe check udev confs...?