I had installed KDE-4.5.4 and nouveau-0.0.16_pre20100615 driver. When i create new user and try to log in i see only black screen and mouse cursor. This is because kde desktop effects are on by default. To fix it i add next to ~/.kde4/share/config/kwinrc in [Compositing] section: Enabled=false Good idea is to make kde desktop effects switch off by default. Reproducible: Always Steps to Reproduce: 1. install kde-4.5.4 and nouveau driver (i'm using this manual: http://en.gentoo-wiki.com/wiki/Nouveau) 2. useradd -m testkde 3. passwd testkde 4. /etc/init.d/xdm restart 5. try to log in only BLACK screen 6. add "Enabled=false" to ~/.kde4/share/config/kwinrc in [Compositing] section 7. /etc/init.d/xdm restart 8. try to log in Success!
Today nouveau-0.0.16_pre20101010 and xorg-1.9.2 was stablized. It seems new versions of nouveau and/or xorg-server can use opengl compositing, so kde-4.5.4 starts successfully.