Hello people:
I have a problem, use Gentoo, and recently installed KDE 4.2 everything worked fine until restart the PC, when I tried typing my username and enter my password, it reload the KDM.
I open the .xsession-errors

KCrash: Application 'kwin' crashing...
QObject: Do not delete object, 'unnamed', during its event handler!
kdeinit4: preparing to launch /usr/lib/kde4/libexec/drkonqi
X Error: BadWindow (invalid Window parameter) 3
Major opcode: 20 (X_GetProperty)
Resource id: 0x160001c
X Error: BadWindow (invalid Window parameter) 3
Major opcode: 20 (X_GetProperty)
Resource id: 0x160001c
Qt: Session management error: Could not open network socket
drkonqi(29509) KFileDialog::getSaveFileName: KFileDialog::getSaveFileName calle$
kwin: Fatal IO error: client killed
kded4: Fatal IO error: client killed
knotify4: Fatal IO error: client killed
kdeinit4: Fatal IO error: client killed
kdeinit4: sending SIGHUP to children.

Sorry for my english.

Please check that your Qt and KDE installations are damaged. Also, which graphics card do you have?
Please also try under a new user. Your configuration might be corrupted.