I've been having this issue on a couple systems, both using the nvidia proprietary drivers and the 12.10 gnome remix.

The screen will go blank even when the power management is set to not shut off the monitor for an hour. It will still try to blank the screen if smplayer is playing a video. The other stupid thing is, about 90% or so of the time, it just blanks the screen and doesn't actually shut off the monitors.

My 2 i7 systems have this issue, one with a Geforce 460 the other with a 560 448 core both experience this issue. The one with the 560 is dual monitors with twinview, but the 460 box only has 1 monitor.

I've been using the 310 drivers, but had this problem on the older drivers. I forget which version Ubuntu wants to install, it's the set not marked as experimental. I needed the 310 drivers for the Steam beta, and they don't seem to have helped or hurt the situation.

Oddly enough I don't get this on my netbook using an nvidia ion GPU and the proprietary drivers.

Anybody have any ideas? FC17 wasn't having this issue, back when I was running fedora. So I know it's not the hardware.