whats wrong with "plasma-desktop-appletsrc"?
the bkp-file is how it should be some crap is adding "[Containments][68]" repeatly
until today it was enough to copy "activityId" to "[Containments][1]", remove the rest and hard restart X so KDE has no chance to write his crap back
well, now after doing that 3 times i still sit in front of a empty desktop witout any widgets