On my 11.3 desktop I was annoyed by what I thought was the screen saver locking my session after an idle period, requiring my password to unlock. Well, I didn’t want this behaviour and it wasn’t supposed to do that, I had disabled every place in the desktop configuration that seemed to be related. I even looked into the KDE4 rc files with a text editor and they all seemed to be in order.
Eventually after some searching I found the answer: It’s the setting “lock screen on resume” in the advanced settings > power daemon. Once I turned it off, it was fine; this desktop doesn’t need suspend+resume anyway.
It seems that this is not a case of counterintuitive naming; it seems that in some configurations there is a bug where a stray event can trigger a screen lock by the powersaved (?). I don’t really understand it, but you can start your investigation here if you are interested:
It doesn’t happen to everybody or every machine, which is why it can be mysterious. So hope this helps if you are having the same problem.