marklp :
I would try the following to solve your problem. If you are using a DVI cable try the monitor with a VGA cable. If your monitor works correctly and dosn't shut down then you mave have a bad DVI cable or the monitors DVI input is bad. DVI cables can be problematic if bent sharply, too long, or of poor quality.
this happened with my old monitor, i have a new monitor now still happens when i use the 16:10 aspect ratio resolutions.
ive used both the dvi and the vga cables both the analog and the digital signal.
the only thing that has stopped it from happening is using the 1280 x 960 resolution.
on my old monitor the aspet ratio would have been 4:3 i think.
i can not fathom why it's happening only that it is.
so the problem occured with two sets of vga cables and one dvi cable on two different monitors with two video cards of the same model for me.
this means it has to be a driver issue a faulty mother board or for some reason the video card is not reading the edid properly and is deciding the monitor can not handle those resolutions OR something is causing it to change teh refresh rate and only rebooting sets it back and it only happens in those resolutions.
so far i have gone about 6 hours using the 1280 x 960 without any problems
im also guessing why for some people it only happens during games or videos.
for normal surfing word processing extra they happen to be using a safe resolution then they go to watch a video or play a game and the resolution changes to one of the problem ones and suddenly they get the no signal problem
and im sure everyone has had that moment where you come out of a game and your screen resolution has been changed to whatever the resolution was in game and you have to reset it to your ussual resolution. my guess is that this is why some people suddenly are getting the no signal untill they have restarted a few times.