that is sad. the only hope i found through all my research regarding this problem is that if you use VGA or DVI, the problem is solved. Which stinks because I love HD. Now you're saying that the problem happens even if connected though DVI. Even now as I'm typing this, my screen just flickered black again. This is very frustrating. I love DELL but ?! Now if ANYONE can just give a straight answer if this monitor issues can be considered as "defective" and can be returned? Because it is obviously not a videocard or pc problem. Too many people with different systems/videocards have gathered here saying they are experiencing the same problem so please  stop going with your default "self diagnostic" answer and give it to us straight while we are still under warranty!

My S2440L problems:
black horizontal lines always flashing and shooting, 1-2 second black screen flashing when someone turns on the fan, ac, lights, etc. I am using HDMI ver 1.4 and I want HDMI because we are not in the caveman age and what the  is the monitor's HDMI port for if you can't use it?!