HowTo – recover KDE desktop after upgrade
02/15/13
Problem – After reinstall PClinuxOS 2012.08 I got a black screen. I did not reformat the home partition as I did not want to loose all my settings and email. Apparently the new install set the root KDE settings correct but not my home KDE settings. I found the repair on the KDE forum – .

Re: upgrade to KDE 4.5 : Black screen – only for account vlaporte
Sat Dec 11, 2010 3:26 pm – KDE forums
It could be that you have compositing enabled but it refuses to work properly.
This is the correct fix.

Try editing
/home/vlaporte/.kde/share/config/kwinrc
from root account (which still workd fine and newuser account also works fine)
in a console without kde running, and look for the section with "[Compositing]"
If you find something like
(or in my case just login as root and open the file with kedit)

Enabled=true
{change to false}
Enabled=false

restart and login - as vlaporte – now KDE desktop works fine
Vince (vlaporte)