Comment # 7 on bug 1060810 from Stefan Hundhammer

OK, that backtrace actually looks good - the Qt UI is waiting for user events
(mouse clicks etc).

Not sure why you can't start it from the KDE menu, though; it should simply use
the appropriate .desktop file and execute the command there.

This should be /usr/share/applications/YaST2/sw_single.desktop .
Can you try to execute the command there? For me, this is

    xdg-su -c "/sbin/yast2 sw_single"

If this fails, please check if "xdg-su" works in general:

    xdg-su -c ls

This should prompt for the root password and then simply execute a "ls" in the
shell you started it from.