It was reported a while back, and I saw it when I underclock my system a few days back. I don't know why your seeing the desktop, the screensaver works no different than how launching MAME games does now. You should see a black background which is hideos.exe. Maybe this process got closed. I assume you tried rebooting, and tried running the screenaver straight away? Still an issue? You may see windows maximizing, restoring but you deffinitly sould not see the desktop. It may be your graphics card showing artifacts of previous video memory. I am almost certain its not affecting everyone.