I downloaded (using Firefox under Windows XP)
xorg-x11-server-Xorg-1.7.7-29.el6.i686.rpm
xorg-x11-server-common-1.7.7-29.el6.i686.rpm
from the 6.1 i386 os filestore,
http://ftp.scientificlinux.org/linux/scientific/6.1/i386/os/Packages/
I then ran rpm with (if I recall well)
rpm --oldpackage -i <rpm file>
(maybe also with --replacefiles)
on each of them and all was well again. I'm not saying this is the
best or even a good way to fix things!

Malcolm

----- Original Message -----
From: "Joseph Areeda" <[log in to unmask]>
To: "Malcolm MacCallum" <[log in to unmask]>
Cc: [log in to unmask]
Sent: Wednesday, 18 July, 2012 3:09:20 AM
Subject: Re: X11 server won't start after yum upgrade

Malcolm,
Which rpm's worked for you?
I have sshd running so I've been able to survive but none of the 
suggestions so far let me log in from the console on my VM.

thanks
Joe

On 07/17/2012 01:41 AM, Malcolm MacCallum wrote:
> I have solved my problem by downloading the relevant rpm files to my
> Windows partition and running rpm with suitable arguments, so I am now
> back to a fully functioning SL with Gnome etc. But it would still have
> been nice to have instructions that worked 'out of the box'.