What version of kdebase-workspace do you have installed?

/usr/lib/libkdeinit4_ksmserver.so is owned by kdebase-workspace 4.8.2-2

Please paste the output of $ pacman -Qi kdebase-workspace

Name : kdebase-workspace
Version : 4.8.2-2
URL : http://www.kde.org
Licenses : GPL LGPL FDL
Groups : kde
Provides : None
Depends On : kdepim-runtime lm_sensors libraw1394 libqalculate qimageblitz polkit-kde consolekit xorg-xprop libxdamage libxklavier xorg-xsetroot libxcomposite libxinerama xorg-xrdb libgles libegl kactivities libxres libxtst xorg-xrandr
Optional Deps : kde-wallpapers: wallpapers for KDE Plasma Workspaces
Required By : kdeartwork-kscreensaver kdeartwork-styles kdebase-plasma kdenetwork-kget kdeplasma-addons-applets-bball kdeplasma-addons-applets-binary-clock kdeplasma-addons-applets-blackboard kdeplasma-addons-applets-bookmarks kdeplasma-addons-applets-bubblemon kdeplasma-addons-applets-calculator kdeplasma-addons-applets-charselect kdeplasma-addons-applets-comic kdeplasma-addons-applets-community kdeplasma-addons-applets-dict kdeplasma-addons-applets-eyes kdeplasma-addons-applets-fifteenpuzzle kdeplasma-addons-applets-filewatcher kdeplasma-addons-applets-frame kdeplasma-addons-applets-fuzzy-clock kdeplasma-addons-applets-icontasks kdeplasma-addons-applets-incomingmsg kdeplasma-addons-applets-kdeobservatory kdeplasma-addons-applets-kimpanel kdeplasma-addons-applets-knowledgebase kdeplasma-addons-applets-kolourpicker kdeplasma-addons-applets-konqprofiles kdeplasma-addons-applets-konsoleprofiles kdeplasma-addons-applets-lancelot kdeplasma-addons-applets-leavenote kdeplasma-addons-applets-life kdeplasma-addons-applets-luna kdeplasma-addons-applets-magnifique kdeplasma-addons-applets-mediaplayer kdeplasma-addons-applets-microblog kdeplasma-addons-applets-news kdeplasma-addons-applets-notes kdeplasma-addons-applets-nowplaying kdeplasma-addons-applets-paste kdeplasma-addons-applets-pastebin kdeplasma-addons-applets-plasmaboard kdeplasma-addons-applets-previewer kdeplasma-addons-applets-qalculate kdeplasma-addons-applets-rememberthemilk kdeplasma-addons-applets-rssnow kdeplasma-addons-applets-showdashboard kdeplasma-addons-applets-showdesktop kdeplasma-addons-applets-social-news kdeplasma-addons-applets-spellcheck kdeplasma-addons-applets-systemloadviewer kdeplasma-addons-applets-timer kdeplasma-addons-applets-unitconverter kdeplasma-addons-applets-weather kdeplasma-addons-applets-weatherstation kdeplasma-addons-applets-webslice kdeplasma-addons-containments kdeplasma-addons-libs kdeplasma-addons-runners-audioplayercontrol kdeplasma-addons-runners-browserhistory kdeplasma-addons-runners-characters kdeplasma-addons-runners-contacts kdeplasma-addons-runners-converter kdeplasma-addons-runners-datetime kdeplasma-addons-runners-events kdeplasma-addons-runners-katesessions kdeplasma-addons-runners-konquerorsessions kdeplasma-addons-runners-konsolesessions kdeplasma-addons-runners-kopete kdeplasma-addons-runners-mediawiki kdeplasma-addons-runners-spellchecker kdeplasma-addons-wallpapers-mandelbrot kdeplasma-addons-wallpapers-marble kdeplasma-addons-wallpapers-pattern kdeplasma-addons-wallpapers-potd kdeplasma-addons-wallpapers-virus kdeplasma-addons-wallpapers-weather kdeutils-kremotecontrol
Conflicts With : kde-common guidance-power-manager policykit-kde kdebase-kinfocenter
Replaces : kdmtheme kde-common guidance-power-manager policykit-kde kdebase-kinfocenter
Installed Size : 74016.00 KiB
Packager : Andrea Scarpino <andrea@archlinux.org>
Architecture : i686
Build Date : Wed 04 Apr 2012 05:01:31 AM YEKT
Install Date : Thu 05 Apr 2012 08:43:39 AM YEKT
Install Reason : Installed as a dependency for another package
Install Script : Yes
Description : KDE Base Workspace

And the output of:
readelf -d /usr/lib/libkdeinit4_ksmserver.so | grep NEEDED

0x00000001 (NEEDED) Shared library: [libplasma.so.3]
0x00000001 (NEEDED) Shared library: [libkworkspace.so.4]
0x00000001 (NEEDED) Shared library: [libkdeui.so.5]
0x00000001 (NEEDED) Shared library: [libkio.so.5]
0x00000001 (NEEDED) Shared library: [libsolid.so.4]
0x00000001 (NEEDED) Shared library: [libSM.so.6]
0x00000001 (NEEDED) Shared library: [libICE.so.6]
0x00000001 (NEEDED) Shared library: [libX11.so.6]
0x00000001 (NEEDED) Shared library: [libXrender.so.1]
0x00000001 (NEEDED) Shared library: [libkdecore.so.5]
0x00000001 (NEEDED) Shared library: [libQtDBus.so.4]
0x00000001 (NEEDED) Shared library: [libQtCore.so.4]
0x00000001 (NEEDED) Shared library: [libpthread.so.0]
0x00000001 (NEEDED) Shared library: [libQtGui.so.4]
0x00000001 (NEEDED) Shared library: [libstdc++.so.6]
0x00000001 (NEEDED) Shared library: [libc.so.6]

OK - so it is not that library but something further down the line that needs it. Is your system completely up to date?

yes, completely
$ ldd /usr/lib/libkdeinit4_ksmserver.so | grep not
libicui18n.so.48 => not found
libicuuc.so.48 => not found
libicudata.so.48 => not found

Please paste the output of $ pacman -Qm

I just installed this to track down what is causing the issue and can not replicate... You will need to figure out which library is linking to the old libicu and report it here.

He's probably using some kde library built from AUR or from some external repository.

$ pacman -Qm
cegui-0.6 0.6.2-8
celt0.5.1 0.5.1.3-1
dump 0.4b43-1
gen-init-cpio 2.6.36-1
hunspell-ru 0.99g5-4
libfetch 2.33-3
ntrack 1:16-2
oxygen-molecule-theme 3.2-1
package-query 1.0.1-1
spice 0.10.1-1
spice-protocol 0.10.1-1
tcp_wrappers 7.6-15
xf86-video-qxl 0.0.17-1
yaourt 1.1-1

nothing related to KDE here. Do you use some external (non official) repository?

This issue is observed on a virtual machine under qemu-kvm. It seems to me I didn't have any kde library built form AUR. From external repository I installed only yaourt and its dependency.
With downgraded icu package to 4.8.1.1-1 all works fine.

I have almost identical installation on x86_64 platform except for real box. There ldd doesn't show any dependency on libicu. Packages versions are the same.

Did you solve? Our packages are fine.