KDE is in a way like 'windows' it has screen savers built in to it as does other os systems
what is going on is this by default it is set to blank out in 5mins time ...
to check this just do like you would in windows 'right click' over desktop
you will see 'configure desktop' select it a panel will come up much like windows on the left is icon 'screensaver' click it then 'uncheck' 'enable screensaver and the desktop should stay on all the time from then on
if not you can use 'set term' command
hope this helps