Shortly but sweetly put: I trashed my KDE4 by attempting to compile a new kdelibs version from source (lesson 1: do NOT try this at home, on a machine/partition that you use on a day to day basis - it's been said many a time, this is a repeat warning)
A little history: I've been running PCLinuxOS since, well, since forever so it seems. After the latest forced reinstall (2009?) I have kept my system updated through Synaptic and have done a few "apt-get dist-upgrade"s in between so you could say I've always maintained my install. Nevertheless, little things crept in that I couldn't get to the bottom of like losing Dolphin/Konqueror thumbnails of camera-raw files - crucial to my photography stuff.
Anyway, long story very short: download, CMAKE, make and make install kdelibs (4.8.0 I believe), CMAKE of kdebase doesn't make it for whatever reason and I do not get back into KDE with the well-known message about "Kstartupconfig error 3". Logged into a failsafe X-session to run Synaptic, reinstalled kdelibs/kdebase from there...no joy
Whatever I did, whichever combination of package reinstall, full remaoval and install etc. etc. , KDE remained aloof and unapproachable error 3 on Kstartupconfig. Tried all the known solutions, including making sure file ownership of the .kde4 directory was set correctly, as well as creating a new user - nothing solved the issue.
Eventually, ready for a reinstall anyway after having backed up my home to an external HDD, I took a drastic action: I first fully removed all KDE packages through synaptic and then I proceeded to remove EVERY SINGLE library file that started with the lettercombination "libk..." from /usr/lib as well as the /usr/lib/kde4 directory. After that I reinstalled KDE4 through synaptic and ...... presto! I'm back in KDE!
Not only am I back in KDE4, my .kde4 settings were intact, I notice an improvement in speed and, as if by pure magic, my raw image thumbnails are back in full glory in all filemanagers!
Now, I am not advising this course of action to anybody but if you are at the point of going for a clean install, this might still be an option sometimes!