I realize this is an odd bug to file, however it has to be said, that when KDE is locked via Kscreensaver's lock session function, a 10 month old bashing randomly on a keyboard is able to cause soem kind of crash in the X server. This may be caused by a buffer overflow but who really knows for sure? But yes, you may want to check into this. Can it be replicated? Yes, just lock your KDE session and bash randomly on the keyboard for 10 minutes. And no he did not hit the power button as the system did not shut down; the X server merely tried to restart and then crashed again.
I appreciate the report, but we merely provide the packages. The KDE developers who write the software are probably the ones you want to let know about this. http://bugs.kde.org