[arch-general] my Arch box randomly becomes irresponsible

Dear Arch users, I have latest Arch installed on my desktop at work. In recent two weeks, the system randomly "suspends" at night (I call it "randomly" because it didn't happen every night. And it seems to happen after a random period idle time) when I am off. I can't wake it up in the next morning thru mouse or keyboard. I tried to disable suspension and hibernation by editing /usr/share/polkit-1/actions/org.freedesktop.upower.policy to change from yes to no But it doesn't work. While I call it "suspend", I am not sure it suspend to RAM or hibernate to disk, because I find the CPU fan and power fan still spin normally. RAM light is also on. So it might be a video driver / setting related issue. For your information, I am using nvidia-302.17-2-x86_64 and have dual monitor set up with nvidia-utils-302.17-1-x86_64 This really bothers me a lot. Any help is appreciated. Thanks! -- Best, Zech