Making a toplevel window transparent (non-opaque) on the following platform fails.

Ubuntu 8.04.3, KDE: 3.5.10, KWin: 3.0, X.org 7.3

Video:

Section "Device"
        Identifier "ATI Technologies Inc RS485 [Radeon Xpress 1100 IGP]"
        Driver "fglrx"
        Busid "PCI:1:5:0"

(xorg.conf is attached)

JDK used to reproduce the issue: 7.0b69, 6u14b07.

It can be reproduced with the following official sun sample:

http://java.sun.com/developer/technicalArticles/GUI/translucent_shaped_windows/TranslucentShapes.zip

The sample allows me to "Enable the per-pixel translucency effect", however the frame shown
is not transparent. The pixels which should be transparent are painted black.