Screen Lock not working without keyboard and mouse hooked up.

For some reason my screen-locking is not engaging when I unplug the USB keyboard and mouse. What should I be looking for to trouble shoot this? I am using KDE.

I am not sure, is there a correlation between input devices being plugged in with the configuration of screen lock. Typically even if the input devices are not plugged in, screen lock might be activated several minutes of inactivity. I could be wrong here.