Bug#605006:

[David Smith <sidicas2@gmail.com>]

Still present in Wheezy. 
Steps to reproduce:

1. Edit your "System Settings" menu item: select "run as different user"
2. Start up System Settings, it prompts for root password, enter it.
3. Click on "Display and Monitor"
4. In the window that pops up, click on "Screen Saver" on the left.
5. Expand one of the screensaver selections in the middle of the screen.
6. Click a screensaver.
7. Segfaults.

This is very similar to bug #688767 that I just filed.   
The "Display and Monitor" section of the System Settings SegFaults *a lot* when run with elevated privileges.

The workaround is to just not run it with elevated privileges.

Crash dump generated by steps above:

Application: KXSRun (kxsrun), signal: Aborted

Using host libthread_db library "/lib/i386-linux-gnu/i686/cmov/libthread_db.so.1".

[KCrash Handler]

#7 0xb77a4424 in __kernel_vsyscall ()

#8 0xb5d64941 in raise () from /lib/i386-linux-gnu/i686/cmov/libc.so.6

#9 0xb5d67d72 in abort () from /lib/i386-linux-gnu/i686/cmov/libc.so.6

#10 0xb5fe6bfc in qt_message_output (msgType=QtFatalMsg, buf=0x96f6740 "kxsrun(5419)/kdeui (kdelibs): Session bus not found \nTo circumvent this problem try the following command (with Linux and bash) \nexport $(dbus-launch) ") at global/qglobal.cpp:2284

#11 0xb71397e8 in QDebug::~QDebug (this=0xbf9efd34, __in_chrg=<optimized out>) at /usr/include/qt4/QtCore/qdebug.h:85

#12 0xb7234fe4 in KApplicationPrivate::init (this=0x9705ee0, GUIenabled=GUIenabled@entry=false) at ../../kdeui/kernel/kapplication.cpp:516

#13 0xb7236050 in KApplication::KApplication (this=0xbf9eff6c, GUIenabled=false) at ../../kdeui/kernel/kapplication.cpp:352

#14 0x0804e74c in ?? ()

#15 0xb5d50e46 in __libc_start_main () from /lib/i386-linux-gnu/i686/cmov/libc.so.6

#16 0x0804f605 in _start ()