I did an update to KDE 4.5 recently, and afterwards noticed that 3D effects were no longer enabled. When I try to enable them from desktop settings, I get a pop up in the panel that says another application is preventing compositing (or something like that).
I have the nvidia 256.53 drivers installed and ‘glxinfo’ says direct rendering is on. I’m also using X server 1.9, but compositing was working with the new X server before I did the update to 4.5.
I had the exact same issue a few days ago on my 11.2 box, what bugged me the most out of it is that there is no log to be found where you at least can find which other application. It was enough to reinstall the nvidia drivers (manually), it happened after this set of updates:
rpm -qa --last | more
sudo-1.7.2-2.3.1 Wed 08 Sep 2010 04:31:34 PM CEST
MozillaFirefox-branding-openSUSE-3.5-8.10.1 Wed 08 Sep 2010 04:31:32 PM CEST
xorg-x11-server-7.4-61.64.1 Wed 08 Sep 2010 04:31:30 PM CEST
xorg-x11-Xvnc-7.4-61.64.1 Wed 08 Sep 2010 04:31:27 PM CEST
MozillaFirefox-theme-oxygen-1.4.90-3.3.1 Wed 08 Sep 2010 04:31:25 PM CEST
wine-1.3.2-2.1 Wed 08 Sep 2010 04:31:22 PM CEST
as I said I did the nvidia update manually, it does an uninstall of the previous install which I am not sure the rpm does, and that fixed it.