This issue i've been having has been plaguing me for weeks now. For some reason, image data from my computer will seemingly cease to transfer to my monitor after an indeterminate amount of time (length varies), resulting in a black screen. I've also noticed that the "device disconnected" sound has played each time a black screen event occurs. As of now, I've determined that my DVI cable is not at fault because the same issue occurred when I replaced it. I also know that the graphics card I use, an nVidia GeForce GTX 550 Ti, is not to blame because the same problem was happening to its predecessor, a GTX 470. I've yet to truly determine if the culprit is the monitor or if there is something wrong with my PC hardware. Can anyone here give me some insight into what might be happening?