KDE Screensaver appears in bottom left
KDE's screensaver seems to have a mind of it's own. 25% of the time it appears in the correct position, covering all of the screen. The other 75% of the time it appears in the lower left, covering only 1/4 of the screen. But, when I move my mouse or press a key on the keyboard, the unlock dialog always appears correctly, in the center of the screen.
How do I fix the problem of the screen saver being positioned incorrectly?
Many thanks, Waldo