I wouldn't be surprised if that's the reason. Or to be more specific: I wonder if it isn't due to the transparency bug that somehow got introduced in KDE 4.0.2. (it wasn't there in 4.0.1.).
It would be interesting if someone has tried it using earlier versions (4.0.1. *and* 3.5.9.) to see if it can be reproduced.
I wouldn't be surprised if that's the reason. Or to be more specific: I wonder if it isn't due to the transparency bug that somehow got introduced in KDE 4.0.2. (it wasn't there in 4.0.1.).
It would be interesting if someone has tried it using earlier versions (4.0.1. *and* 3.5.9.) to see if it can be reproduced.