Dell U2715H monitor. I am having almost exactly the same problem described in this thread:
Monitor serial #: CN-0VGTFG-64180-52S-0SRL A01
I'm using it with a computer I built.
Windows 8.1
Video card is an EVGA GeForce GTX 970 SSC ACX 2.0+
Drivers are the latest Nvidia ones (353.30 as of this writing)
It has four DisplayPort outputs, one HDMI, and one DVI. I am using the DVI output to drive a Samsung BX2440X monitor (which works fine, which is why I'm thinking this is a monitor problem). and the regular DisplayPort to mini DisplayPort cable included with the monitor to connect the U2715H.
I've tried all of the default Windows 8.1 power plans - High Performance, Power Saver, and Balanced.
Operating at 2560x1440.
Purchased monitor through Amazon.
Things I've already tried:
-Uninstalling Dell Display Manager software.
-Disconnecting the monitor's built-in USB 3.0 hub.
-Ran a monitor self-test.
I've had the monitor for about 6 weeks. For the first month or so, I had it plugged by the HDMI input to the mini-HDMI output on my old video card, which was an MSI Twin Frozr II GeForce 560 Ti. Everything was fine until last week, a few days after I got the new video card (GeForce 970), which upgrade was necessary to really do the monitor justice at native 2560x1440 resolution.
This problem is absolutely maddening. It didn't happen at all over the weekend, and hasn't yet happened today. It'll go away for a few days or hours, then happen again. Doesn't seem to have any correlation to how long the machine has been running. I usually let the machine go to "sleep" overnight, but sometimes it stays on all night with just the display asleep (e.g. if I have a video paused or the computer is in High Performance power saving mode).
I was on the phone with Dell technical support earlier, but we got cut off and there doesn't seem to be any way to call them back and pick up where we left off. Very, very frustrating.
I'm running out of ideas here. Anyone got something I haven't tried?