After emerging kde-base/kdebase-meta-4.1.2 I was unable to start it or use any of it's applications. It turned out, that folders /usr/share/kde4 /usr/share/mimelnk and /usr/share/applnk had permissions 700. Running "chmod -R go+rX /usr/share/mimelnk /usr/share/kde4 /usr/share/applnk" and kbuildsycoca4 fixed problem.
Created attachment 168368 [details] emerge --info
Created attachment 168370 [details] xsession-errors of failing KDE4 start with wrong /usr/share/kde4 permissions
*** This bug has been marked as a duplicate of bug 239269 ***