1. I selected openastromenace-lang package. YaST added also openastromenace and openastromenace-data.
2. After that I seleted openastromenace package and in context menu I clicked on "undo".

Result:
xmessage dialog with the following message:
cat: write error: Broken pipe
YaST got signal 11 at YCP file /usr/share/YaST2/clients/inst_packages.ycp:49
/sbin/yast2: line 421: 16777 Segmentation fault   $ybindir/y2base $module "$@" "$SELECTED_GUI" $Y2_GEOMETRY $Y2UI_ARGS

I can reproduce the problem regularly. 

Package:
nikman@linux-nikman:~> rpm -qi yast2-2.16.71-6.1
Name        : yast2                        Relocations: /usr 
Version     : 2.16.71                           Vendor: SUSE LINUX Products GmbH, Nuernberg, Germany
Release     : 6.1                           Build Date: Sat 07 Jun 2008 08:15:59 AM MSD
Install Date: Tue 10 Jun 2008 04:31:05 PM MSD      Build Host: cimarosa.suse.de
Group       : System/YaST                   Source RPM: yast2-2.16.71-6.1.src.rpm
Size        : 3206436                          License: GPL v2 or later
Signature   : DSA/SHA1, Sat 07 Jun 2008 08:18:07 AM MSD, Key ID a84edae89c800aca
Packager    : http://bugs.opensuse.org
Summary     : YaST2 - Main Package
Description :
This package contains scripts and data needed for SuSE Linux
installation with YaST2

nikman@linux-nikman:~> rpm -qi yast2-packager-2.16.53-3.1
Name        : yast2-packager               Relocations: /usr 
Version     : 2.16.53                           Vendor: SUSE LINUX Products GmbH, Nuernberg, Germany
Release     : 3.1                           Build Date: Sat 07 Jun 2008 08:58:55 AM MSD
Install Date: Tue 10 Jun 2008 04:32:09 PM MSD      Build Host: poincare.suse.de
Group       : System/YaST                   Source RPM: yast2-packager-2.16.53-3.1.src.rpm
Size        : 1611419                          License: GPL v2 or later
Signature   : DSA/SHA1, Sat 07 Jun 2008 09:00:39 AM MSD, Key ID a84edae89c800aca
Packager    : http://bugs.opensuse.org
Summary     : YaST2 - Package Library
Description :
This package contains the scanner/parser and dependency checker for all
packages handled by YaST2.



Authors:
--------
    Klaus Kaempf <kkaempf@suse.de>
    Stefan Schubert <schubi@suse.de>
    Arvin Schnell <arvin@suse.de>
Distribution: openSUSE 11.0 (X86-64)

nikman@linux-nikman:~> uname -a
Linux linux-nikman 2.6.25.9-0.2-default #1 SMP 2008-06-28 00:00:07 +0200 x86_64 x86_64 x86_64 GNU/Linux