I have a dual monitor setup, using the proprietary Nvidia drivers. I modified the screen saver in System Settings to 10 minutes and to blank the screens. After that in 10 minutes of no usage the screens do blank. However thereafter, after I move the mouse to reactivate the screens, after about a minute or so the right screen will blink off for a couple of seconds and then come back on again. It will stay on for perhaps 30 seconds or so and then keep repeating this pattern of a couple of seconds off and 30 or so seconds on. I then restart the system and will see a small window that is black. Sometimes there are as many of those black windows as there were repeating cycles of the screen blanking.
I changed from blanking to using the clock as the screen saver with the same thing happening, but this time the small black window would have the clock in it. I modified the screen saver to not come on, but this continues to happen, ignoring the fact that the screen saver is not enabled. So, I again enabled the screen saver but gave it a time of 1000000 (one million) minutes before activating, but to no avail. After an initial 10 minutes of no usage the screen saver comes on, and then again after reactivating the screen after a minute or so the cycle of off/on will start again.
So, it seems that once activated I am unable to deactivate the screen saver in addition to the fact that it doesn't work right. I also redid the nvidia-settings but that changed nothing. Somewhere in the bowels of KDE config files there is something I need to disable/turnoff. Any ideas?