Web search hasn't turned up anything diagnostic for this.
User has a 2008-era 30" Apple Cinema Display with a newer workstation running Ubuntu 12.04. Video card is GeForce GTX 550 Ti. Keyboard and mouse are Apple, plugged into the USB2 port on the back of the monitor.
Problem: the system will sometimes power down the screen randomly. Worse, when the system sleeps overnight, the monitor can't start properly the next morning - the keyboard or mouse or power button on the Cinema Display all wake up the monitor into a "flashing" state, where it turns off and on again about once every half-second or so. Temporary fix: unplugging the power brick on the monitor for a second or two will straighten it out - but we have to do it fast, or the box no longer recognizes the keyboard or mouse. If we're fast enough, it will pick up the mouse and keyboard again after about 10 seconds.
Up to this point, it seems like a hardware problem in the monitor or power brick, maybe age-related. Here's the kicker: he has a older, second workstation running Ubuntu 8 that never shows this problem - the problem only arose when we switched to the new box. If he uses the old box along with NX to screen-share into the U12 box, there are no problems at all. However, we want to retire his older box - right now he's only using it to keep his monitor working.
Display issues aren't an area we know much about. Assuming we don't want to buy newer screens, keyboard, and mouse that are known to be compatible (since it "works" under the right setup, that seems wasteful), we're not sure how to debug this, except by leaving his Frankensystem intact for now.
EDIT: Just to be clear, we're willing to go into the weeds - for example, I'd like to know if there are any standard tools for observing communication between the OS / video card and the monitor that I could try when this problem occurs.