It seems that my monitor getting older and older has problems with return to the normal state after dimmed display / saving energy mode. It can’t wake up and I have to switch it off, wait a few minutes and they try again. Very annoying.

I unchecked ‘dim screen’ / ‘screen energy saving’ in Power Management settings but it does not work. I have OpenSuse 12.2 – is it related to that system, KDE or is it hardware specific?

This very much sounds like a Hardware issue, especially since you have to wait for your monitor to cool down before the display turns back to normal.

You should seriously consider to get a new display.

You’re right, Mamarok. The most probable problem is with a broken capacitor. I had my display repaired. I’ll let you know how it goes.