I just received a used PowerMac G4 a few days ago and had problems installing OS X due to installation errors and the fact that it kept randomly going to sleep. Well, I finally got it installed, but it's still continuing to go to sleep on me, even while I'm using it. Sometimes I can use it for five minutes, sometimes only a few seconds. It never freezes up, it only sleeps and I can always wake it back up. Any ideas about what could be going on?