Sometimes, in KDE 4.13.3 (as shipped with Kubuntu 14.04 LTS), I cannot enter anything into the password field of the locker, nor can I press any buttons with my mouse. I use the following workarounds for this issue:

• triggering suspend-to-RAM by closing my laptop's lid (not sure if this the default configuration, maybe you have to set it up first) and then resuming


• if the above does not work, I switch to a "real" console with e.g. Ctrl-Alt-F1 (this by itself has to work, of course) and kill the locker process with killall kscreenlocker_greet

The actions mentioned above will not disable the locker but they at least make the input work again.

One might also want to have a look at this KDE bug report for possibly better workarounds (did not have time to evaluate them yet).