"shutdown applet in kde4 does not work"

Binary package hint: kdebase

I cant shutdown my PC. The shutdown buttons doesnt work. I can only shutdown in the Terminal with: "sudo shutdown -h now"
reboot works too with "sudo shutdown -r
But I want the normally way back. Whats the problem with my PC?

I have kde4

9.10 (karmic koala)

ProblemType: Bug
Architecture: i386
Date: Sun Jan 17 16:30:59 2010
DistroRelease: Ubuntu 9.10
InstallationMedia: Kubuntu 9.10 "Karmic Koala" - Release i386 (20091028.5)
NonfreeKernelModules: nvidia
Package: kdebase (not installed)
ProcEnviron:
 LANGUAGE=
 LANG=de_DE.UTF-8
 SHELL=/bin/bash
ProcVersionSignature: Ubuntu 2.6.31-17.54-generic
SourcePackage: kdebase
Uname: Linux 2.6.31-17-generic i686