My approach is to download "xscreensaver". It's in Synaptic. It is usually launched through terminal - "xscreensaver-demo". This brings up the interface. Display mode - select "Disable Screensaver". Then click on advanced - uncheck "Display Power Management". It's worked on all versions of PCLinuxOS that I've tried.
You need to install your own screensaver software to take control of this issue. There seems to be no way to change the "default". Or at least I can't find one and have taken the proactive approach of installing my own and then taking control of it. Works for me.
By the way, if you are into astronomy maybe you want to check out
http://www.pclinuxos.com/forum/index.php/topic,85914.0.html