I am also getting this problem with the blanking screen after 10 minutes - I have noticed that it is only if the KDE desktop has been loaded. After a reboot, and if you don't load KDE desktop, the problem does not occur. Then, as soon as you go into KDE desktop for whatever reason, and then watch media later, the blanking occurs. I assume it's something to do with the screensaver?
Is this a known problem? How do I submit it as a bug if it is not known?