Hello.
I'm experiencing same problem after update to openSUSE 11.4 and, consequently, to KDE 4.6.0.
I tried to move (and remove at last) /tmp/kde* and /var/tmp/kde* firectories. After logout/login panel reverted to normal but after system restart (I beleve, kdm restart will also lead to this) panel became black again.

Several remarks: when panel is black, vertical resizing helps for duration of session. Second - for me panel goes black again when it's vertical size is 28 points.

Is there any news on this bug?

I can confirm that this is NOT limited to a specific theme (rather it occurs with many themes using transparancy) and is NOT limited to Intel graphics (I have the problem with Intel and ATI graphics here).

Below you can find two screenshots:
1) Desktop effects on: http://img600.imageshack.us/img600/3066 ... ectson.png
2) Desktop effects off: http://img62.imageshack.us/img62/3120/d ... ctsoff.png

I created a brand new user, the problem occurs as described:
Log in, turn off desktop effects (all is fine), log out, log back in.
From now on, the panel stays black with desktop effects disabled!

I am using OpenSuSE 11.4 and KDE 4.6.2

Have you tried KDE 4.6.3? I'm not aware of any bugs in relation to this - but it could be caused by compositing taking a while to start on your system. Do you use KWin?