I had this problem with Mandrake 9.2 and 10 (now I use Debian Sarge, which is fine). If you build kdeartwork-screensaver from source then apparently it fixes it (XScreenSaver detection seems to be broken in Mandrake's packages). I just disabled the KDE screensaver and used xscreensaver instead (although this meant I couldn't use the extremely pretty Euphoria -_-)
Anyway, try building the screensaver package from source.
Veni, veni, venias
ne me mori facias!