I recently upgraded to KDE 4.8 on my opensuse 12.1 machine.
And boy is KDE 4.8 fantastic. My laptop has never run so smoothly and does not heat up at all compared to 4.7.
Anyway, coming to the point. Yesterday I saw that my screen is turning off after around 2-3 minutes of inactivity(watching a movie/utube).
I checked the power profiles and Screen turn off option is unchecked, DIm Display is unchecked. I have turned off the screensaver. I could not get it to not stop turning off the screen.
I disabled the Power management settings and it worked for a while. To test this, i turned off the screen using the power button(which is set in the profile) but this issue cropped up again.
You just add the last line under the heading shown and save the file. If you have the 3D graphic driver loaded this should work, but may not work if you only use 2D.