I found a solution:
1. The problem occurred on a machine using a nvidia graphics card running under the nvidia driver.
2. KDE4 effects were inoperative until adding the following to /etc/X11/xorg.conf:
Option "Composite" "Enabled"
3. Openoffice now displays correctly.
The reported bug must be some odd side-effect of KDE4 with the nvidia driver. It's beyond me, but now it works!