Are there anything in the logs from the time it shutdown?

What distro are you using, I've had this problem with breezy.

dylunio

Hm, it may be a coincidence but supermike had a very similar problem. He is using xscreensaver blank screen and it also locks up.

I wonder if you guys use the new Xorg 7? I have experienced lock ups occassionally with that although only on some 3D screensavers or programs like celestia and some games. It seems Xorg 7 isn't entirely stable yet.. or maybe it is latest xscreensaver that is a bit unstable. In that case you could try gnome-screensaver as an alternative (as suggested by free-zombie in the other thread).

But I'm just guessing. Your problem could well be something entirely else.

Looking at the logs should help indeed.. with most of such problems.

I'm currently using Debian stable (so XFree86 4.3 i think is the version) but i've had this problem on other distros before (Gentoo is one of them, i think) I'm not using any screensaver programs or anything, it's just blanking

i checked XFree86 log and the last thing it says is

SwitchToMode - Succeeded
GetModeLine - scrn: 0 clock: 54000
GetModeLine - hdsp: 640 hbeg: 688 hend: 744 httl: 900
vdsp: 480 vbeg: 480 vend: 482 vttl: 500 flags: 37

Hm, that unfortunately doesn't tell me much. What about what's in /var/log/messages.log ?

Thanks

I didn't find anything significant in /var/log/messages. I left the monitor on and in console (while X was running on tty7) and it didn't lock up tonight (it did blank out though, i think)

Perhaps it's a problem with your video driver. There might be multiple drivers available, search here.

I'm using the proprietary nvidia driver :\
i've fixed the problem by just switching to tty2 when i go to sleep, but it would be nice to know what is causing the problem

I'm guessing the proprietary driver. I've heard many bad things about that, and you're not even allowed to fix them.