I posted this issue first to http://scientificlinuxforum.org/index.php?act=ST&f=16&t=1803

Here is a copy/paste for your convenience:

> I have been happily using SL 6.0 for about a year now, happily running on my Mac in a Parallels Desktop virtual environment. 
> What works: 
> SciLinux 2.6.32-220.23.1.el6.i686 #1 SMP Mon Jun 18 09:58:35 CDT 2012 i686 i686 i386 GNU/Linux
> xorg-x11-server-Xorg Version : 1.10.6 Release : 1.sl6
> Parallels Desktop 7.0.15104(778994)
> Mac OS X 10.6.8 (10K549)
> 
> About 1 month ago, some updates were issued through one of 
> epel Extra Packages for Enterprise Linux 6 - i386 6,306
> rpmforge RHEL 6.0 - RPMforge.net - dag 4,448
> sl Scientific Linux 6.0 - i386 4,630
> sl-security Scientific Linux 6.0 - i386 - security updates 2,180
> to update the kernel, xorg, MySQL, and a few other applications. 
> 
> After a lot of trial and error, I have installed all updates except for:
> 
> kernel.i686 2.6.32-279.1.1.el6 sl-security
> kernel-devel.i686 2.6.32-279.1.1.el6 sl-security
> kernel-firmware.noarch 2.6.32-279.1.1.el6 sl-security
> kernel-headers.i686 2.6.32-279.1.1.el6 sl-security
> xorg-x11-drv-ati-firmware.noarch 6.14.2-9.el6 sl-security
> 
> If I install any of these updates, I can boot into single user just fine, but the system hangs where the character graphics stop and the xorg graphics normally begin. If Parallels sends a shutdown or reboot message, the system shuts down normally most of the time so the kernel is not infinite looping
> 
> /var/log/messages shows a variety of errors, usually after the system has started shutting down but I don't entire trust them.
> 
> I can live with this. I am mostly reporting it for the benefit of others, but if some one has an idea, I would be interested. 
> 
> In the mean time, I am going to make a backup copy of the virtual disk, and upgrade to SL6.2 just to see if that helps.  

and

> After upgrading to SL 6.2, startup halts at the same place.
> 
> In the /var/log/Xorg.0.log file, I see that the Parallels video driver "prlvideo" cannot load because it includes an undefined symbol: "miEmptyData". The Parallels mouse driver cannot load because of the undefined symbol: "dixScreenOrigins".
> 
> Then Xorg aborts because it cannot find any screens. 


I am not sure it is a SL bug.  Parallels is known for being behind the cutting edge.  But I don't think of SL as cutting edge either.

I have also posted this to the Parallels support forum here: http://forum.parallels.com/showpost.php?p=633981&postcount=9

-=O=- Randy