Comment 12 for bug 708151

I got this issue too upgrading Kubuntu 10.10 with KDE 4.6 from PPA's backport: black screen, x errors,...

I tried a lot of thing to understand the origin of the problem (error message was not very usefull).

The problem was linked to the new kdm theme. It was triying to use ethais (previous defaut KDM theme). Ethais folder and background .png seems exists but are corrupted files (/usr/share/kde4/apps/kdm/themes/ethais). All needed part of ethais are not in the folder (and are, in this state, in the last 4.6 kde package of KDM -purge and reinstal kdm package dont change anything)...

To use the new 4.6 kdm theme, i changed manualy "ethais" to "horos" in /etc/kde4/kdm/kdmrc

After that, and rebooting kdm worked fine...

(similar issue about kdm: https://bugs.launchpad.net/ubuntu/+source/kdebase-workspace/+bug/517803)

(In my configuration -nvidia chipset-, i also edit /etc/X11/xorg.conf to charge the "nouveau" module...)