I might have a solution, although we've got 2 different problems. You seem to be able to get into KDE.. it the K-apps that fail. My KDE core wasn't loading... I couldn't even get to my desktop after I supplied a login and p/w. I managed to get around it.
Instead of using the source for the kde-libs and kde-base files and compiling, I grabbed the RPM's. Then I FORCED them in... Now it works fine
rpm -ivh kde-libs.whatever.rpm --force
give 'er a try