I have a HP W2338H that is flashing black a few times, then back to normal.
It's plugged to a xfx hd 6750( i think ) via hdmi @ 1080/1260. It ran normal through dvi. I'm not over clocking but running my CPU max all the time.
I have noticed it seems to happen when my downstairs neighbors turn on there washer, dryer or anything that uses alot of power. But that just may be nonsence. Also recently installed a corsair 600w PSU if that matters to the issue.
Actually, you ought to try and run it at the factory set resolutions and see if this occurs...
1920 x 1080
Usually it shouldn't.
The monitors are certified to not cause electronic interference, although, you need to check if your neighbors washer comes upto that level of certification
Anyways, give it a try at the 1920x1080 Resolutions and give us a feedback.