Just bought a Asus desktop and had issues with my screensaver working. Spent 1/2 hour on tel with teck support, got nowhere. Found out that wireless mouses still emit a signal even when still. Have a Microsoft Wireless Laser 6000. Worked fine but....no screensaver. Googled my mouse, went on the software update. found out there was an update for the 6000 for windows 7, downloaded it and badabing presto! Screensaver works. All my other presets for turning monitor off after so many minutes, works, hybernation, works. Good to go. So my problem was the Mouse.(no more cheese hehe).
Hope this helps.