I have Radeon X550 running KDE4 and have a minor issue of flickering on all of my fullscreen applications. So, this morning I googled and found the problem. It was caused by the behaviour of KDE4 (and other compositing manager such as Compiz) to cancel redirection of fullscreen applications to improve performance. This is by the fact that all fullscreen application does not need any effect because it would fill all the screen.

So, this is what [LPAD] suggest:

How to resolve the problem: – open with your favourite editor this configuration file: .kde/share/config/kwinrc -under [Compositing] section add: UnredirectFullscreen=false – If you have no [Compositing] section create it, on the top of the config file, and then add the option under it. – save and exit – Press ALT+F2 to open krunner, then write into it: kwin –replace – No flickering/crashes anymore! 😉

REFERENCE: [LPAD] Masucci, Geovanni. (KDE) Fullscreen applications flickering with effects ON. https://bugs.launchpad.net/ubuntu/+source/kubuntu-default-settings/+bug/327199 (snapshot taken 10 June 2009)