Version: unspecified (using KDE 4.6.0) OS: Linux With kms and opensource ati driver the transparency doesn't work properly if blur is activated. Panels and other things like the kde menu look dark and are not transparent. Reproducible: Always My graphics card is a 4890. I've found other people, who have ati, that have the same issue. It's a bug you notice instantly, and it's very annoying.
So why do you believe the bug is in KDE, instead of the ATI drivers?
clearly a driver bug. Please upgrade to Mesa 7.10 or change the strength level of blur effect to workaround the issue or just disable blur.