I am fairly new to Linux but a pretty fast learner. I am currently booting three different distros, each having a different desktop environment, trying to decide which I want to settle in with. For me this is one of the biggest annoyances about KDE and it keeps me going back to Xfce or Gnome. It's really too bad, KDE has a lot of great things going for it (after you get rid of the windoze-ish appearance -that's like keeping a photo of your ex! lol)but this particular bug is so annoying it pretty much offsets it. Btw I've tried everything mentioned here and it's still a rare moment when my screensaver has a chance to kick in. Gnome and Xfce do exactly what I tell them to all the time(which is what a machine is supposed to do!) I'm going to probably have to fire KDE for the third time and move something else into this partition. Sure wish they would fix this thing.

I gather you have checked the Power Management settings in System Settings > Advanced?

Have you tried this at all? I had to do this on one of my machines:

$ setterm -powersave off -blank 0

From
http://www.cyberciti.biz/tips/linux-dis ... blank.html

I had the same problem: console does not blank, but when X is running it blanks after 10 minutes of being idle. I tried all the solutions mentioned in this thread without success.

Ultimately this fixed it:

xset -dpms

Hope this helps!

As a side note - I also tried everything in this thread, having the same issues....
I have not yet restarted/reloaded kde, but the screen hasn't blanked out since running the xset -dpms command, as mentioned above...

THANKS RONNIE!!!

xset -dpms

works for me.

I had blank screen problem occurring as a result from waking up laptop from sleep without power cord plugged; plugging it afterwards caused the screen go blank with KDE message: "Compositing has been suspended by another application. You can resume using the 'Alt+Shift+F12' shortcut".

And the key combination actually works for me.