The basic problem of this error is that KDE can’t load kstartupconfig because of some configurations in Gnome effected the KDE .You can fix this error by
open konsole or gnome-terminal and write
- chown username.username -R /home/username/
- this changes the file owner and group and operate on files and directories recursively which allows you to start kde-desktop with the kstartupconfig
Thats all