Version:            (using KDE 4.4.0)
Compiler:          gcc 4.4.3 
OS:                Linux
Installed from:    Archlinux Packages

Hello, 
I can force kscreenlocker to segfault and unlock the desktop every time. Jus by pressing and holding the Return key. The unlock prompt freezes for a minute and then kscreenlocker segfaults

$ /usr/lib/kde4/libexec/kscreenlocker --forcelock

kscreenlocker(21765)/krunner main: app  0   0   false   0   0
kscreenlocker(21765)/kdecore (KSycoca) KSycocaPrivate::openDatabase: Trying to open ksycoca from  "/var/tmp/kdecache-username/ksycoca4"
kscreenlocker(21765)/plasma LockProcess::readSaver: mForbidden:  false
kscreenlocker(21765)/plasma LockProcess::createSaverWindow: Saver window Id:  37748770
kscreenlocker(21765)/plasma LockProcess::startHack: Starting hack: "kblankscrn.kss -root"
kscreenlocker(21765)/plasma LockProcess::loadGreetPlugin: GreeterPlugin  "classic"  ( classic ,  Username + password (classic) ) loaded
kscreenlocker(21765)/krunner LockProcess::x11Event: MapNotify: 37748770
kscreenlocker(21765)/krunner LockProcess::x11Event: not fully obscured
kscreenlocker(21765)/krunner LockProcess::x11Event: not fully obscured
X Error: BadAccess (attempt to access private resource denied) 10
  Major opcode: 2 (X_ChangeWindowAttributes)
  Resource id:  0x2400022
kscreenlocker(21765) KxkbCore::settingsRead: Kxkb is disabled, exiting... 
kscreenlocker(21765)/krunner LockProcess::x11Event: MapNotify: 37748776
kscreenlocker(21765)/krunner LockProcess::x11Event: not fully obscured
kscreenlocker(21765)/krunner LockProcess::x11Event: no plasma; saver obscured
kscreenlocker(21765)/krunner LockProcess::x11Event: not fully obscured
kscreenlocker(21765)/krunner LockProcess::x11Event: no plasma; saver obscured
Authentication failure
Authentication failure
Communication breakdown on read
Communication breakdown on read
Communication breakdown on read
Communication breakdown on read
Communication breakdown on read
Communication breakdown on read
Communication breakdown on read
Communication breakdown on read
Communication breakdown on read
Communication breakdown on read
Communication breakdown on read
zsh: segmentation fault  /usr/lib/kde4/libexec/kscreenlocker --forcelock

This is KDE SC 4.4. I did not try it with my previous installation of KDE 4.3.